I was just daydreaming of a great idea! Just make surfboards like skateboards in how you can you can use them on the map. However, surfboards don't stop moving until you reach land or deselect them. And of course, they can only be used in shallow to mid shallow water.

Also, the GFX of your character holding the skateboard/surfboard under his arm would be cool. The up and down GFX of the board can be default since you don't see the bigger side.