I'm a recreational diver. I wouldn't use this as my _only_ computer, but I would say the same for the computers I currently use. I always dive with 2 computers just in case one fails, a battery dies, etc. As 'latchkey said, never rely on a single piece of equipment. With that being said, I would be willing to swap out my wrist computer for the Apple Watch Ultra. The superior display and UX would actually be a big quality of life improvement over my current wrist computer. And, I'd still have my backup computer in my SPG to compare against or fall back to.
Slight clarification: the Apple Watch Ultra has a water resistance rating of 100m. The Oceanic+ app has a 130ft/40m limit because that's the recreational diving limit.