It is fantasy-arcade-like in that you don't need to focus too much on your diving setup or health. You could literally pet the fish or zap them with your ray gun to "heal" the sick or agitated ones. Your oxygen seemingly never ran out. The whole point was to explore, chill out, and learn about sea creatures. With the amount of painstaking detail they put into the fish, environments, and education I'm sure they're not just going to throw you into a space with great whites, goldfish, and narwhals all around you.
I just hope it's a full-fledged game and not just about the online play. I lived for completing the encyclopedia. The treasure hunting was a huge time sink as well with hundreds of items to find with your little treasure detector. You could teach your pet dolphin tricks, customize an aquarium with the fish you've encountered, and even decorate your own personal reef to attract all types of fish. I really hope all that comes back, plus we get the online stuff, but it's too early to tell.