DRINKING & EATING:
A fry can eat and drink there own habitat to help hydrate I bet they never get headaches or get dehydrated.
Without water they would not be able to swim around or even live!
HUNTING & PLAYING:
One way a fish might play is hunting even though it is hard it is probably lots of fun.
An ocean is like a huge toilet bowl for them. They drop off there waste as they swim!
The fry has many more uses for water but these are some of them that I came up with!