Well, how about parasail surfboarding?
Inflated boat racing? Jet ski racing?
Rock and waterfall climbing? I don't believe I have seen a cliff adequate to bungee off of safely.
We could rig up a sliding cable across one of the canyons?
We could kayak off of several waterfalls. Also white water rafting.
Some great swells on the westward side of the island.
It would also be easy enough to create some bicycle paths for speed racing too.