Use the arrow keys to guide the whale.
Left-right and up-down work as expected.
Press A and Z to swim towards the front or the back.
Press K to shift between keyboard and mouse control mode.
All credit is due to NickyNouse for the original super-cool project concept. All I did in this remix was simplify the code for the swimming behavior (and add the ability to toggle between keyboard and mouse control).
If you like this project, here's one with a jumping behavior: