Watersports is a side-mission of 8 courses with the Jetski unlocked after the mission Say Cheese. The Jetski is always available behind the film studio at Prawn Island triggering the mission and upon completing each course the next one is unlocked. The player is rewarded with $500 after all the courses are passed and the Wetsuit outfit is unlocked.
The name of the side mission is a sexual reference. "Watersports" is an alternate terminology for urolagnia, a sexual fetish for urination.