This is a really fun interpretation of the theme! It's clear you made quite a system, I had a good time playing with the simulation mode and was surprised you could make waves that have different peaks. The art is pleasant, I like the color palette and seeing all the different swimmers! The water calmly moving up and down instead of being static is a really nice detail as well.
Some feedback from me: I think you should bind movement also to WASD, I kept instinctively trying to use that instead of the arrows keys. You've got a good sound for the wave going, but I think a nice big splash sound and a little screenshake when the player hits the water would help sell the feel of the game! I'd also consider speeding the wave up a little bit, you have to wait quite a while between waves.
Awesome job!