One of the options for getting around coastal eastern Laconia is the Flying Dolphin Hydrofoil, calling at Plaka, Kiparissi, Gerakas and Monemvasia. Probably calls at more places in peak season.
We watched this one arrive at Gerakas, load up, turn round and zoom off at a fair old speed.
2007 update: This service no longer operates down this eastern coast, leaving the locals somewhat isolated and the tourist trade diminished.