If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Upwards arrow key - jump.
Downwards arrow key - dive.
I always wanted to know what it was like to be a shark and now I can with this awesome game! Go on a killing spree and don't feel bad about it because you are a born meat eater! Plus hey, they shouldn't be in your home right, after all the sea is your domain! Launch yourself on innocent passengers on the boats bobbing in the sea above. Fun!