Scuba diving is a fundamentally dangerous and expensive hobby. I don't know if this will make a big dent in the cost of a dive. FWIW a snorkel and a pair of fins are pretty cheap. For ~$50 you can have a lot of fun swimming around exploring coastal ecosystems without needing to stress about signals, equipment, safety stops, or any of that stuff. This is a lot closer to democratizing diving than anything else.

Although I am not the biggest fan of subscription models I am not sure pushing the cost down of dive computers will help democratize diving. I can't imagine it's a very cheap hobby to begin with.

Also, a quick glance, dive computers seem to be $400+, many are $1000+. The watch in question is $800 and I feel like people who are into diving aren't the type of people who find an $800 prohibitively expensive.

You can definitely get a solid dive computer for under $400, and the $1000+ are going to have features that won't be present on the Apple Watch Ultra, like air integration, lower depth ratings, etc.

Paying other people to take you diving can get pretty expensive quickly, but the dive professionals themselves generally do not make a lot of money. It is one of those things that people do professionally because they love it, not because it pays well. (Speaking only about recreational diving here, industrial diving is a whole different beast.)

Most people use dive computers in range of 200-300$, so a subscription based 700$ Apple device isn't democratizing anything, it's just bringing rent seeking to another market.