The layout of Jost [1], and the number of nearby cays, makes the area ideal for kayaking. Armed with food, water, sunblock, and plenty of energy, visitors can craft their own expeditions. If you are going to paddle away from shore, be sure to equip your kayak with a flag or other marker to catch the eye of passing motorboats. A collision between a kayak and motorboat off Jost Van Dyke in 2002 killed an American tourist and demonstrated that accidents can, in fact, happen in paradise.
If high-powered water sports are more your cup of tea, you can rent water skis or jet boats or even spend hours bouncing on a huge trampoline over the water at White Bay [2].
Links:
[1] http://www.moon.com/destinations/virgin-islands/jost-van-dyke
[2] http://www.moon.com/destinations/virgin-islands/jost-van-dyke/sights/south-shore/white-bay