Loved the art and sfx. "Shark" "Dun dun dun" made me laugh while I played. I thought you did a great job keeping the game simple and clean.
Some minor improvements: Maybe adding a progressive element to the difficulty of the sharks would help keep the game interesting or even adding power-ups that float in with the sharks, causing the player to decide between killing an oncoming shark or taking the powerup. And yes, there was also the issue of no final score, but I don't care too much about score anyway, I'm just here for the game :)
That being said, I think you did awesome! This is actually one of my favorite games I've played on here so far out of the 40+ I've rated. Nice job and keep up the pleasant graphics and humorous sounds!