The direct answer: only Garmin Descent Mk3 and Suunto Ocean are certified dive computers built around decompression algorithms; Apple Watch Ultra 3 is water resistant to 100m with a depth gauge, but it isn’t marketed or certified as a dive computer the way the other two are. Between the two real dive computers, Descent Mk3 goes deeper (200m rated) and costs more ($1,200); Suunto Ocean is rated to 60m, costs less ($899), and has the longer battery life of the pair.
At a Glance
- Best for serious/technical diving: Garmin Descent Mk3 — 200m dive rating and diver-to-diver messaging (with the Mk3i and a transceiver accessory).
- Best value dive computer: Suunto Ocean — genuine EN 13319 dive certification at $899, with the longest battery life of the three.
- Not a dive computer, but a strong everyday rugged watch: Apple Watch Ultra 3 — great for snorkeling and swimming, not built or certified for decompression diving.
Garmin Descent Mk3: The Deepest-Rated, Most Feature-Dense Option
Descent Mk3 (43mm) runs $1,200 and is rated to survive and operate at depths up to 200 meters, with up to 48 hours of battery life specifically in dive mode. It’s built on Garmin’s Fenix 7-derived design with a new AMOLED display, and adds Dive Readiness scoring (a dive-specific take on Garmin’s Training Readiness metric) alongside the brand’s usual endurance and sleep tracking.
Its standout feature is diver-to-diver messaging via SubWave sonar technology — though that specific capability requires the Mk3i variant paired with a separate Descent T2 transceiver accessory, not something the base Mk3 does on its own out of the box.
Suunto Ocean: Real Dive Certification at a Lower Price
Suunto Ocean (All Black model) is priced at $899 and carries genuine EN 13319 dive-computer certification to a maximum operating depth of 60 meters — the same regulatory dive-computer standard category as Garmin’s watch, just at a shallower certified depth. It runs the Suunto Bühlmann 16 GF decompression algorithm for dive planning, supports wireless tank pressure display and freedive-specific modes with separate underwater and surface views, and includes 115+ general sport modes.
Battery life is the strongest of the three here: up to 60 hours in dive and everyday use, 50 hours with continuous multi-band GPS tracking, up to 16 days in daily smartwatch mode, and up to 26 days in standby — genuinely competitive numbers for a device that’s also a certified dive computer.
Apple Watch Ultra 3: Rugged and Water-Capable, But Not a Dive Computer
Apple Watch Ultra 3 costs $799 and is water resistant to 100m with a built-in depth gauge and water temperature sensor — genuinely useful for swimming, snorkeling, and casual water exposure. But Apple does not market or certify Ultra 3 against the same dive-computer regulatory standards (like EN 13319) that both Garmin and Suunto’s watches carry, and it lacks a dedicated decompression algorithm built for planning scuba dives.
That doesn’t make Ultra 3 a bad watch — it’s an excellent everyday rugged smartwatch with real water capability, satellite messaging, and the deepest iPhone integration of any watch on the market. It just isn’t the same category of product as the other two for anyone planning actual scuba dives with decompression stops.
Spec Comparison
| Garmin Descent Mk3 | Suunto Ocean | Apple Watch Ultra 3 | |
|---|---|---|---|
| Price | $1,200 | $899 | $799 |
| Dive certification | Rated to 200m | EN 13319, rated to 60m | None — 100m water resistance only |
| Dive-mode battery | Up to 48 hrs | Up to 60 hrs | Not applicable (no dedicated dive mode) |
| Smartwatch-mode battery | Not the primary use case | Up to 16 days | ~42 hrs (72 hrs low power) |
| Decompression algorithm | Yes | Yes (Bühlmann 16 GF) | No |
| Phone compatibility | iOS and Android | iOS and Android | iPhone only |
Prices are approximate, current as of publication, and change frequently — confirm the latest price with the retailer before buying.
So Which One Should You Actually Buy?
If you’re a certified diver planning real scuba dives with decompression stops, buy Garmin Descent Mk3 or Suunto Ocean, not Apple Watch Ultra 3 — the depth rating and decompression algorithm are the whole point, and Ultra 3 simply doesn’t offer either at a certified level. Between the two, Descent Mk3’s 200m rating and diver messaging suit technical or deep divers, while Suunto Ocean’s 60m rating comfortably covers recreational diving at a lower price with better battery life. If you mainly swim, snorkel, or want a rugged everyday watch with occasional water exposure, Apple Watch Ultra 3 is genuinely excellent — just don’t buy it expecting dive-computer functionality it isn’t built or certified for.
How We Compared
We did not physically test all three devices underwater for this comparison. Specs and certification claims were verified against each manufacturer’s own current product pages and press materials, cross-referenced with 2026 hands-on coverage from Wareable and dive-focused retailers. More on our process is on our editorial standards page. Prices are approximate, current as of publication, and change frequently — confirm the latest price with the retailer before buying.
FAQ
Is Apple Watch Ultra 3 safe to use for scuba diving?
Apple doesn’t market or certify Ultra 3 as a dive computer, and it lacks a built-in decompression algorithm. For actual scuba diving with decompression planning, a certified dive computer like Garmin Descent Mk3 or Suunto Ocean is the appropriate tool — always follow your dive training agency’s guidance on required equipment.
What does EN 13319 certification actually mean?
It’s a formal European regulatory standard for dive computers and depth gauges, covering accuracy and reliability requirements. Suunto Ocean carries this certification; Apple Watch Ultra 3 does not.
Which dive computer has the best battery life?
Suunto Ocean, rated up to 60 hours in dive and everyday use and up to 16 days in smartwatch mode — ahead of Garmin Descent Mk3’s 48-hour dive-mode rating.
Can Garmin Descent Mk3 send messages to other divers underwater?
That specific diver-to-diver messaging feature (SubWave sonar) requires the Mk3i variant paired with a separate Descent T2 transceiver accessory — it isn’t included on the base Mk3 model by default.
Comparing Ultra 3 against other rugged watches instead? See our adventure smartwatch comparison. Browse more in our Wearable Tech category.
