No camp or cable park in the Tokyo area that I know of. I do know that wakeboarding is very popular there though. If you can, check out places like Ashinoko and Eidogawa near the tokyo area. If you have transportation and can get out towards the Mt Fuji area, there's Lake Yamanaka and Lake Kawaguchi. Both have tow services there. Lake Kawaguchi, at the base of Mt. Fuji, is one of the most beautiful places I've ever ridden.