Snorkeling and scuba diving are possible during the clear-water December–April season. That’s when California-based scuba instructor Douglas Storms (Juárez 187B, tel. 323/285-1418, www.divingbeyond.com ) offers snorkel and scuba lessons and excursions out of his Adventure Center headquarters, a block from the Estero El Pozo dock. Off season, you can contact him in Sausalito , California (tel. 415/331-7925 or 415/325-3789).