I know personally, I love underwater travel and animals. Hytale showing the underwater scene hyped me up, but I am hoping larger creatures will be added. Is there anything any of you want to see in the game?
I agree with you completely, I have a massive interest with the ocean and I see very few games that dive deep in the development of making underwater scenery. If they add a lot of additions with their seas (such as sea creatures, treasures, underwater cave systems and more) as well as a realistic diving system (such as scuba diving suits or snorkels to breath just above the water) it will be a perfect game for me.
I would love to have more personalized ways to play the game. Such as if you were more into exploration, you could have lighter armor, that let you move faster, but possibly didn't help you as much with damage. If you were more into fighting bosses, you could wear BIG Tank armor, but that would slow you down more. And if there were suits and tools that would help with specific things, such as a wetsuit for underwater or wings suits that you could glide. Not quite a elytra where you can fly, but a way to fall slower.