You've taken a simple concept and added a lot to it. The art is quite well done, I liked the water rippling effect. Good choice on having a Vs. AI mode, made it more accessible to people rating.
Endless mode was maybe a bit too hard from the get-go, as you basically have to jump as soon as you press start to avoid being completely knocked off. Felt the kicking could have had more impact, maybe a sound effect and some particles when you land a kick. But good job overall!