OX FROG300 Depth Rainbow Review

When you think about dive watches you automatically envision watches that look like a Rolex Submariner or Blancpain Fifty Fathoms. Dive watches have been around for over seventy years and are by far the most popular style of watches produced. In all those decades the design, look and functionality of dive watches really hasn't changed at all. Basically you have a round watch with a high contrast dial and a uni-directional dive time bezel. So when a dive watch comes out that looks like no other watch before it, I immediately take notice.

One such watch released last year from the brand OX named the FROG300. The FROG300 features a rarely seen asymmetrical case with destro set crowns along with added technology to help rescuers indentify recovered divers. Before we get more into the details of the FROG300 let's go over the history of OX Tool Watches.



The concept for OX was first conceived by founder Joseph Bolart in Almeria, Andalusia in 2021. Bolart set out to create a near perfect dive watch and believed his background in mechanical engineering and industrial design would allow him to achieve this goal. Bolart is also an extremely accomplished diver and is a NAUI (National Association of Underwater Instructors) instructor. Bolart found a love of watches through his grandfather, so with OX Joseph is able to combine his professional skills and passions in one project.

Over the next two years Bolart and his team set out to make their vision a reality. Bolart along with Stephane Levesque (CEO), Eric Yongda and Sky Ma (Production Facilities) used their experience in the watch world as well as manufacturing and engineering to see the original concept become a tangible watch on July 4, 2023 with the introduction of the FROG300 dive watch. Over the next year the FROG300 was further refined and went through some evolutions before finally being delivered to their first customers in 2024.



While headquartered in the United States, OX watches are manufactured in Shenzhen, China using Japanese produced movements. Shenzhen is starting to become a major production center for not only mass produced watches, but also very technically advanced watches such as the FROG300. This allows OX to keep prices in check and also end up with a high quality end product. OX watches are produced in low volumes which is imperative to ensuring all watches are thoroughly tested and pass tight quality control standards before they leave the factory.

Initial Thoughts

After seeing some pictures of the FROG300 Depth Rainbow I started looking more into the brand and specs of the FROG300 series. It became very obvious that the FROG300 was a watch I had to get into my hands sooner than later. I reached out to Joseph Bolart and asked if it would be possible to get a FROG300 in for review and he said it would be his pleasure. Soon after a FROG300 Depth Rainbow arrived.



After unboxing the FROG300 Depth Rainbow, the first thing I noticed was the color of the grade 3i titanium case. This is the first watch I've seen that uses grade 3 titanium, you mostly see grade 2 or 5 and Blancpain uses grade 23. While grade 3 is still pure titanium, it offers more strength than grade 2 while still maintaining the awesome deep grey look of pure titanium. The grade 3i titanium is 15% harder than standard grade 3 titanium by having its crystalline structure compressed during the casting process. It's no secret that I'm a huge fan of titanium watches and own many personally. Also for the size of the FROG300, the watch feels light and very well balanced on the wrist. The deep grey satin look of the watch also enforces that is a true tool watch.

The next thing I noticed about the FROG300 was the excellent rubber strap and titanium deployant clasp complete with micro-adjustments. The Depth Rainbow comes with a yellow strap that goes well with the colors of the dial. The "No Deco" time limits scale is also printed on the strap for easy reference to avoid the need for decompression strops. While a functional addition to the strap, the table also really drives home the fact that the FROG300 is a serious dive watch. The rubber strap needs to be cut to size and has slots between the spring bar holes to easily cut straight with a pair of scissors. I took off one section from each side until I found a fit that was good for me. I also positioned the clasp in the middle of the adjustable range so that I could make the watch larger and smaller with my ideal fit being in the middle. Underneath the titanium deployant clasp there is a level that when pressed in will allow the clasp to expand or contract by around 15 mm. Having an adjustable deployant clasp is a game changer and I wish more brands would offer them.



The final thing I noticed about the FROG300 Depth Rainbow during my initial time with the watch was the Depth Rainbow dial. There are numerous models in the FROG300 range that have a more traditional inner rotating dive bezel featuring 0 to 60 minute increments, but the Depth Rainbow goes a bit on its own here. While 0 through 40 is the normal dive scale with 0 to 20 having a blue background and then alternating between grey and black for each 5 minute period until 40, everything changes after 40. At 45 there is a red block to represent 5 meters, at 50 there is an orange block for 9 meters, at 55 is a yellow block for 18 meters and finally there is a green block for 27 meters. As you reach each designated depth the color will change to blue, this is a visual indicator of how deep you are. Not only is this something I've never seen on a watch and is very useful, but it also adds a ton of richness and color to the dial.

Technical Specifications

Now that we've gone over my initial impressions of the FROG300 Depth Rainbow, let's now take a look at the technical specifications of the watch. As mentioned before the watch is crafted out of grade 3i titanium and has a case diameter of 45 mm with a lug to lug length of 51.4 mm. At its thickest point the FROG300 is 16.8 mm tall and weighs in at 135 grams when sized for my 7.25 inch wrist. For its size, the FROG300 is rather lightweight and wears its weight well. The thickness I recorded also includes 1 mm added for the NFC disc on the case back and domed sapphire crystal.



The FROG300 uses a double domed sapphire crystal with an anti-reflective coating applied to the inside of the crystal. This is beneficial since being a dive watch, the sapphire has a high chance of getting banged up against foreign objects. Anti-reflective coating is rather easy to scratch, so not having any on the exposed crystal allows the sapphire to stay highly scratch resistant while still having the benefits of an anti-reflective coating.

Underneath the crystal clear sapphire crystal is a matte black dial. At twelve o'clock you have a blue OX logo and at 6 there is "Automatic GMT WR 300M / 1000ft ID+SYS" printed in grey. The FROG300 uses applied oval hour markers that feature W9/X1 Super-Luminova that appear white in normal lighting and glow a strong green in low light. Centrally mounted are four hands that signal running seconds, hours, minutes and GMT. The hour and minute hands are oval shaped to match the look of the hour markers, and the seconds hand is also capped off with an oval tip. The hour hand glows a matching green to the hour markers while the minute and seconds hands glow a matching blue to the first 20 minutes of the inner rotating dive bezel, which makes sense since these two hands are crucial for diving. The minute hand tracks dive time while the seconds hand makes sure the watch is running during a dive.



The GMT hand is done in red and is arrow shaped which glows an orange-red in low light. The GMT hand is short enough to not really affect any crucial time telling abilities and only has the possibility of blocking the black backed date window at 8 o'clock. In between the hour markers is a 24 hour scale printed in red that is used in conjunction with the GMT hand. I typically do not use a GMT function, but on a dive watch it actually does make sense, especially on a professional style dive watch. It is very common for less casual dives to take place in a foreign area away from your home time, so having a GMT function on a dive watch like the FROG300 fits.

Finishing off the dial is the inner uni-directional dive bezel. From 0 to 20 minutes the background of the bezel is done in blue with white text with each 5 minute increment receiving an Arabic numeral. For 25, 30, 35 and 40 the background alternates between grey and black. Starting at 45 there are a series of four blocked areas that are done in red, orange, yellow and green. Each color is paired with the following depths: 5M-15ft (Red), 9M-30ft (Orange), 18M-60ft (Yellow) and 27M-90ft (Green). This "Depth Colorgraph" is very easy to use as each color will change to blue as its indicated depth is reached signaling how deep you currently are. This is a simple yet very effective depth gauge as opposed to what you see in complicated mechanical depth gauge watches from brands like Jaeger-LeCoultre and IWC. The color of each depth also adds a nice dose of color to the dial and gives the watch its Depth Rainbow name.



Moving on from the dial is a rather thick but proportionate bezel devoid of any markings except for "DIVE TIME" being engraved into the bezel pointing to the blue crown at 10:30 that operates the dive bezel. The entirety of the case has the dark grey titanium color with a satin media blasted finish. The case shows that the watch is an all business tool watch and gives off zero reflections.

Looking head on at the watch you can see that the FROG300 has an asymmetrical off-centered design to it. Normally I'm not a fan of this style of design on anything from cars to clothes, but it works here. The majority of the case resides to the left of the center of the lugs. I'd say the center of the dial lines up about twenty-five percent of the way down the lugs going left to right. In addition to the bezel controlling crown at 10:30 there is also the time setting crown with large crown guards at 8 o'clock. Visually this design really makes an impact and is unlike anything else I've seen in the watch world.



Looking at the profile of the watch you can see that while the lugs are rather short they point nicely down contouring to your wrist. On my 7.25 inch wrist, the FROG300 fit perfectly and I feel those with smaller wrists should be able to pull off the watch as well. Remember this is a serious dive watch, so legibility is key here, the watch should be larger than a typical daily cuff friendly wearer. The right hand side of the case features FROG engraved into the case filled in with white. This reminds me of my Blancpain Fifty Fathoms 500 Fathoms with Blancpain engraved on the side of the case. I know some people do not like this design cue, but I actually do.

The left hand side of the watch features a nicely scalloped black screw down crown topped with a Gold Ion Plated cap with the OX logo. This crown is located at 8 o'clock and is flanked by oversized crown guards. Once un-screwed this crown can manually wind the automatic movement in the resting position. Pulling the crown out to position one lets you advance the local time hour hand and can also be used to more quickly advance the date. Pulling the crown out to position two allows you to set the time and advances both the local hour and GMT hands, where crown position one only advances the local time hour hand. Position two also stops the seconds hand for precise time setting. Pushing the crown back in causes no jump in the minute hand and screwing the crown back in doesn't require any additional care to get the crown to catch and screw down.



The blue crown at 10:30 also offers the same ample grip as the black crown and features an OX logo on top as well. This crown does not screw down and only turns in one direction to ensure your dive time is never accidently lengthened for the safety of the diver. The bezel turns with not too much force needed and advances the internal dive bezel by one minute increments.

Finishing off the left hand side of the case is a "GMT Adjust" engraving pointing to the black crown and arrow engravings around the blue crown showing which direction to turn the dive bezel crown. Finally there is an automatic helium relief valve found between these two crowns. Which how serious of a dive watch the FROG300 is, having a helium relief valve allows the FROG300 to be used by professional saturation divers.

The rubber strap is secured to the lugs using FKM housing screws that use special o-ring washers that prevent them from getting unscrewed. OX provides special tools with the watch that allows you to remove the strap. The lug width is 22 mm and the FKM rubber strap tapers down to 18 mm at the titanium deployant clasp. The Depth Rainbow comes on a yellow rubber strap with the "No Deco" timing chart printed on it. Both sides of the strap feature a triangle motif cut out of them that adds some visual interest to the strap. The back of the strap has some ribbing that keeps the strap in place on your wrist as well.



As mentioned previously the rubber strap is cut to fit. On the back of the strap there are cut out lines that you can follow with a pair of scissors to make sure you cut a straight line. I ended up taking off one piece at a time and alternating sides until I found a size that worked for me. If you will be using a wetsuit with the watch it would make most sense to put the clasp all the way in to get your wrist size. This will allow for 15 mm of expansion to fit over a wetsuit. Since I will not being using the watch with a wetsuit, I put the clasp in the middle position and then sized so that I'd have the most room for adjustment for my wrist sans a wetsuit.

The clasp is crafted out of matching grade 3i titanium and has two black pushers that are used to release the clasp. Underneath the clasp is a lever that when pushed in will allow the clasp to ratchet in and out to get precise fitment of the strap. The clasp allows for 15 mm of adjustments to the total length of the strap, which should cover most lighter weight wetsuits as well as allow for your wrist to expand and contract.



Flipping the watch over shows off the solid case back. The case back is gold ion plated and features a ring with most of the important specs of the watch engraved into it. In the center void of the case back is the serial number of the watch which is used to register the watch with the ID+SYS system along with an engraving of a frog. The void in the back of the case is then filled with a blue plastic disc that screws into the case back and features an NFC chip. This disc adds about 1 mm of thickness and 1 gram of weight to the watch. Using the ID+SYS system the owner of the watch can add such crucial data as blood type, allergies, spoken language and a picture of themselves to help medical personal in the situation where the wearer is unable to communicate. The NFC chip can be accessed by a phone close to the case back and reveal the important medical details of the wearer. With the screw down crown and case back the FROG300 is rated for 300 meters of water resistance.

Underneath the case back beats the Japanese made MITOYA (Citizen) 9075 automatic movement personalized for OX. The 9075 beats away at 28,800 vph (4Hz) and has a power reserve of 42 hours. The movement is rated with an accuracy of +15/-10 seconds per day and on our timegrapher it showed an accuracy of +3 seconds per day when averaged out over several positions. This result is much better than the quoted accuracy and even inside of chronometer specs. The functions of the watch are hours, minutes, seconds, date and true GMT.



On The Wrist

The OX FROG300 Depth Rainbow arrived at the perfect time to go on a trip with us to the coast. The last time we took a trip to the coast I ended up taking two dive watches, but decided this time to only take the FROG300. Before we left for the trip I wore the watch out while we went to drop our dogs off at camp to make sure it would be comfortable being my sole watch for nearly a week.

It took a few minutes to get used to the crown at 8 o'clock, but after that the watch wore extremely well on wrist. While 135 grams isn't exactly featherweight, the watch wears its weight well and is a fraction of what it would weigh if crafted out of stainless steel. In all honesty the watch did pretty much disappear on my wrist after extended wear times. The wide rubber strap required zero break in and kept the watch nice and centered on my wrist. During the five hour drive the coast, the watch never become an annoyance or caused any wrist fatigue.

Being the Texas coast, the entire time we were outside the weather was extremely hot and humid. This makes your wrist swell up pretty quick. When you go back indoors and spend time in the low 70s your wrist then contacts again. This typically leads to a situation where a watch fits perfectly inside but then gets way too tight when you're outside. Luckily the FROG300 has a clasp with micro-adjustments which let me easily size the watch up or down to best fit my ever changing wrist size.



In everyday life most people have their phones with them and they are the most convenient way to check the time. While at the beach or in the pool a watch really becomes a vital device again. Having younger children we don’t want to spend too much time in the sun, so it's extremely nice to have the time on your wrist at all time to monitor when it's time to get out of the sun. In the pool and in the ocean the FROG300 was just a perfect companion. The watch had great legibility underwater and naturally had no problems handling the splashing of two and a half year olds. The watch just also looks like it should be in or near the water at all times.

To test visibility I use a simple method of glancing at a watch while driving to see how easy it is to tell the time. With ten hours of total driving time I had ample time to try this test out. Being a purpose built dive watch, it's no surprise that the FROG300 easily passed this test. Also in low light conditions the watch just glows with the ample amount of Super-Luminova present on the dial. Even in lightly shaded areas I noticed that lume of the watch was glowing, this is only something I have witnessed on my Fifty Fathoms 500 Fathoms, which is the most lumed watch I have ever experienced, so that's saying a lot.



On my 7.25 inch wrist with a 55 mm flat area the 51.4 mm lug to lug length of the OX FROG300 fit my wrist perfectly. The watch covered my wrist nicely and never favored one side over the other. The watch is actually a bit thinner than the measurements suggest since 1 mm is for the blue NFC disc and another 1 mm or so is due to the doubled domed crystal. The watch actually looks very proportionate when being worn.

The watch fit in very well with the coastal environment and was just as at home in the pool and at the beach as it was at a nice dinner. Unless you live near the beach I wouldn't think the OX FROG300 would be an everyday wearer and the color scheme of the Depth Rainbow isn't the most subtle. A black strap would probably tone the watch down a lot and the other dial colors wouldn't be as colorful as the Depth Rainbow. Personally I love the loud colors and even more so since they actually serve a purpose. This really is the perfect summer / vacation watch aesthetic in my opinion.

Being a colorful and loud watch it's not shock that the FROG300 Depth Rainbow is no wallflower of a watch. While wearing it I could tell a ton of people were looking at it. I had a few people approach me at the beach and at the pool asking about it. Everyone loved the asymmetrical look of the watch and thought the depth color scale was such a cool feature. Given the titanium construction people were also blown away with the price of the watch.



Value and Position in the Market

Speaking of price, the OX FROG300 Depth Rainbow retails for $1,720 on the rubber strap. For that price you're getting a grade 3i titanium watch with a truly unique look and interesting color depth gauge function. The watch is running an extremely accurate movement with a very useful GMT function as well. The NFC ID+SYS technology could also be a life saving feature for those that are more adventurous with their watches. Now would be a good time to look at other watches that share similar specs and features to the FROG300 and see how it compares value wise.

First up we have the T50 from Sinn. This watch is crafted out of titanium and has a 41 mm case diameter and a uniquely placed crown at 4 o'clock. The T50 has a depth rating of 500 meters and runs on a Swiss made Sellita SW300-1 automatic movement. The T50 is much more of a traditional dive watch with no special features like GMT or the depth gauge scale. The T50 is a lot more expensive than the FROG300 at $3,970.



Next we have the Pelagos Ultra from Tudor which is also crafted out of titanium and has a 43 mm case diameter. The Pelagos Ultra has a standard dive watch design but does feature a unique lumed adjustable clasp. The Pelagos Ultra is rated for 1,000 meters of water resistance and comes with a manufacture movement. The Tudor is much more expensive than the OX at $6,100 and doesn't feature any extra functionality past time and date.

Moving on we have the Seamaster Planet Ocean 600M from Omega which is crafted out of titanium and has a case diameter of 43.5 mm. The watch has a depth rating of 600 meters and is powered by an in-house movement. Once again the Planet Ocean offers no extra functionality and features a helium relief valve at 10 o'clock. The Planet Ocean is much more than the FROG300 at $8,600.

Finally we have a watch that is close to my heart, the Fifty Fathoms 500 Fathoms from Blancpain. The 500 Fathoms has a 48 mm case crafted out of titanium and is rated for 1,000 meters of water resistance. The watch is powered by an in-house movement with 120 hours of power reserve and has an extremely luminous dial. The watch has an automatic helium relief value at 10 o'clock and doesn't feature any additional functionality past time and date. The 500 Fathoms is much more expensive than the FROG300 at $29,100.



Looking at these four titanium dive watches shows just how good of a value the OX FROG300 Depth Rainbow is. While the Tudor, Omega and Blancpain offer either manufacture or in-house movements, they don't offer much features wise to beat the OX. While all four watches offer higher water resistance ratings than the FROG300, recreational diving stops at 40 meters and even professional divers hardly ever go past 100 meters. 300 meters is more than enough for even the most extreme of divers. The unique design and very useful features of the FROG300 really makes the watch stand out, even in a field of very respected and extremely well built dive watches. The price of the FROG300 also means it’s a watch that you don't have to be scared to take into the water. On the other hand, I'd be petrified to take my 500 Fathoms into the pool just in case a seal was damaged and I'd be facing a service bill more than the FROG300 retails for. Not to mentioned I'd be scared to hit the watch on anything.

Closing Thoughts

So in the end is the OX FROG300 Depth Rainbow for me? Without a doubt, the FROG300 is 100 percent for me. The watch checks off most of my personal wants in a watch. Over 50 mm lug to lug, titanium construction, unique design, rubber strap and an adjustable clasp. During my week with the FROG300 on my wrist at the coast the watch really felt like a watch I'd have in my collection. At times I think I even forgot that it wasn't actually one of my personal watches.



Would I recommend the FROG300 to somebody looking for a purpose built dive watch? I would in an instant. The FROG300 just excels at what it was meant to be, a "near perfect dive watch". Being created by a professional diver, the FROG300 started out on footing not normally seen when a watch brand sets out to create their dive watch. Everything the watch does is to be better at its job of being a companion for a diver. The low light visibility is off the charts and the colored depth gauge is something that can be used during dives. Even the printed "No DECO" table on the strap is useful to divers that don't have it memorized or forget it during a stressful dive. The case being made out of hardened grade 3 titanium not only looks great and is lightweight but also protects the watch from scratches often seen on grade 2 titanium cases.

While I'm not a fan of the GMT function, it actually does make sense to be added to a professional dive watch where the wearer will typically be diving in a destination that does not share their home time. The NFC ID+SYS addition is also a nice bonus to the package and if the medical staff is aware of the system could be a life saver for the wearer. Even moving the crowns to the left hand side of the watch reduces the possibility of the watch getting snagged on obstacles while diving. It does sound like Joseph and the team at OX have really thought of pretty much everything a dive watch should be while developing the FROG300.



While I am not an avid diver and can count the number of times I have scuba dove on one hand, I do see how the watch would be appealing to more serious divers to be a back up to their dive computers. For me the OX FROG300 Depth Rainbow would make the perfect summer and vacation watch though. It's tough, accurate and just looks the part of a watch that should live at the beach.

I would really like to thank Joseph and OX for sending us this FROG300 Depth Rainbow to review. The watch made quite the impression on me and I really bonded with it over the course of our trip to the coast. Needless to say this will be one of the watches I really don't look forward to sending back.

For more information about the FROG300 Depth Rainbow please visit : OX Tool Watches

Technical Specifications

Reference Number: OXF3-YEBMTI-DEPHT

Retail Price: $1,720

Case Size: 45 mm

Lug to Lug: 51.4 mm

Thickness: 16.8 mm (With Domed Crystal and NFC Disc)

Weight: 135 grams

Case Material: Grade 3i Titanium

Bezel: Grade 3i Titanium

Strap: Yellow FKM Rubber Strap with Titanium Deployant Clasp with Micro-Adjustments

Movement: MITOYA (Citizen) 9075 Japanese Made Automatic

Functions: Hours, Minutes, Date, Seconds, True GMT

Power Reserve: 42 Hours

Water Resistance: 300 Meters