West of Guánica via Route 116 then 304 south, the fishing village of LA PARGUERA is best known for its bioluminescent bay, or La Bahía Fosforescente . It also affords some of the best diving in Puerto Rico at The Wall , about five miles offshore. Around La Parguera you could lose yourself amid the maze of mangrove swamps, channels, canals and offshore islands and cays. The village itself makes a pleasant hub from which to explore the region, with a good sampling of pleasant accommodations, decent restaurants and a lively bar culture.

Like Mosquito Bay on Vieques, La Bahía Fosforescente is a mangrove swamp illuminated at night by millions of organisms called dinoflagellates, which light up when disturbed. Years of tourist infestation, and resultant environmental abuses, however, have diminished the luminosity here, compared to Mosquito Bay, but boats (charging US$5) still leave every night from La Parguera pier at 7.30pm and 12.30am. Unlike others tours, Alelí Tours (tel 787/899-6086) will let you swim for a while in the water, an experience which makes you feel as if you're gliding through the Milky Way.

Divers are drawn to La Parguera's innumerable coral reefs offshore, many of them still unexplored. The Wall runs from Guánica to Cabo Rojo and drops to depths of 2000 feet, with visibility up to 120 feet. Snorkelling, too, is excellent; barracudas, morays, manatees, nurse sharks and sea turtles abound. Contact Paradise Scuba (Rte 304 in town, tel 787/899-7611) or Parguera Divers at Parador Posada Porlamar (tel 787/899-4171) for equipment and details on expeditions.

Kayak rentals are available from Alelí for US$10-15 an hour and US$50-60 a day. In case you're not up for a workout, you can also rent Boston whalers with slow engines for about the same price from Cancel Boats at the town docks (tel 787/899-5891)