Sea Ventures Dive Copamarina (Copamarina Beach Resort, Carr. 333, km 6.5, 800/468-4553 or 877/348-3267, www.divecopamarina.com , daily 9 a.m.–6 p.m.) runs day and night dive excursions ($65–119) to sites including the 22-mile-long Guánica Wall, the Aquarium, and the Parthenon, a coral formation featuring a variety of sponges. Daily snorkeling excursions go to Gilligan’s Island, Cayo Coral Reef, and Bahía de la Ballerna ($55 including equipment). Certification courses are offered. Also available are kayak, catamaran, and paddleboat rentals.
San Jacinto Boats and Seafood (Carr. 333, 787/821-4941) rents sea kayaks and equipment for diving and snorkeling. It also operates a ferry to Gilligan’s Island every hour on the hour Tuesday–Sunday (high season) 9 a.m.–5 p.m. or Friday–Sunday (low season) for $5. Dine on fresh seafood dishes while you’re there.