Thanks for playing! Glad you had some fun swimming and eating tuna! It's quite tricky to get the deeps ones, as you have to manage both air and energy.
Interesting, I don't know why pressing the keys quickly would do that. It's possible you ran out of energy? Each body movement takes 1 energy, and each tuna restores 25. If your energy gets to 0, you're no longer able to move. Maybe that's what happened?