H2O: Just Add Water - Season 3 Episode 5

Zane has bought motorbikes to earn rent from clients, but also organizes a rugged range race, offering $1,000, confident to win himself. He actively recruits competitors, greedy for their $200 entry fees, including Will, who has to borrow the cash. Learning Will has experience from his parent's Andes posting, bad loser Zane enlists Nate to cheat roughly, but fails. Will's precise recollections about the aggressive moon pool tentacle help Lewis devise a test which shows the key is mixing water from the ocean itself and the waterfall, albeit apparently very weak except at full moon.