Along with fishing, swimming, sharks, seamonsters, ships, cannons, etc. Let the age of high seas piracy begin! avast ye and prepare to be boarded!
I definitely find some of these to be a little over the top but you get the idea. How awesome would it be to build your own ships or floating houses and go straight up water world with the whole experience. I think it would add an incredible amount of depth and originality. I'd love to wake up on my floating house or ship and sail to land to deal with the harsh realities that wait on the main land. Because lets not forget, you still need to go to land to get resources. You can even have pirate clans. I think just starting with building things on water would help it take off. I wouldn't even have a problem with keeping water as lethal.