Might be an unpopular opinion as I see a love/hate here for the Apple Watch Ultra. Add to this, the fact I'm just guppy new diver so please know my opinion might be irrelevant.
I've owned an AWU already and for me, it makes sense to use it for the time being until I feel like I need something more advanced. Sure, it requires a subscription but I got my subscription during Black Friday for something like $50.
I too am relatively warm, shallowish diver and for right now, it's filling the need. This is only a solid use case if you own an Apple Watch Ultra or have an Apple Watch and want to upgrade to the Ultra.
My own experience: The app is decent on the phone and a nifty place I can log dives. I get a hiccup here and there with changing the name of the dive and there's some other quirks I've sent to Huish that it'd be cool to see.
The app on the watch is pretty good for what I need. Time, depth, compass, water temp, NDL, alarms for too fast ascent, alarm for safety stop, and I'm sure pretty conservative so as not to get sued. It's super bright and easy to read even deep(ish) at 60 or a smidge deeper.
Complaints that are minimal: I'll get an alarm and I'll see too fast ascent in my app if my arm goes above my head for any reason. Post dive info in the phone app isn't accurate for minor things, i.e., starting tank pressure and ending tank pressure uses a sliding bar so my fat fingers can't get it precise. Doesn't have an average depth as a metric. Will have other pertinent info and you can move your fingers over the dive profile and you can give it a good guesstimate.
Again, my typing could be moot if you don't have an AW or AWU already!