Apple support doc talks about using the Depth app on the Apple Watch Ultra

Don’t replace your deep dive watch with an Apple Watch Ultra just yet. Apple has published a new support document detailing how to use the Depth app that measures water temperature, duration, and depth to 130 feet (40 meters).

From Apple’s support doc: Underwater activities are risky. The Depth app isn’t a dive computer and doesn’t provide decompression stop information, gas analysis, or other recreational scuba diving functionality. If you’re using Apple Watch Ultra where the failure of the device could lead to death, personal injury, or severe environmental damage, always use a secondary depth gauge and timer/watch. Before going on a dive, be sure your Apple Watch Ultra is free of cracks or other damage.