The 13,226-hectare Parque Nacional Marino Isla Bastimentos is shaped like a bridge, and as its name suggests, most of it is underwater. It starts among the mangrove islands on the southwest side of Bastimentos, arcs across its midsection, and curves down to two lovely little islands.

These islands, the Cayos Zapatillas, are the most visited parts of the park thanks to the good snorkeling and diving among the nearby coral gardens and underwater caves, which start about 12 meters down. It’s quite dramatic even to snorkel around here; the shallow waters suddenly give way to deep canyons. The coral heads inside the reef are in good shape, and there is a large variety and abundance of fish. Nurse sharks live in this area, as well as two different species of lobsters.

Note that it’s turbulent around here, which can make visibility cloudy. It’s not a good place for snorkelers who aren’t fairly strong swimmers. There’s an attractive beach on the western island for those who would prefer to lounge, but the chitras (sand flies) can get nippy. The Zapatillas are about an hour by fast boat from Isla Colón.

There is an interpretive trail called El Bosque Detrás del Arrecife (literally, “the forest behind the reef”) on the more easterly of the Zapatillas (farther away from Bastimentos). It starts behind the ranger station. ANAM has put out a glossy booklet, in Spanish only, that describes the trail. Good luck finding a copy. Camping on either island is possible for US$5 more per tent.

Most visitors to Isla Bastimentos come only for the beach, but the inland forest is a natural treasure trove, which is why a big swath of it is included in the marine park. For one thing, it is home to 28 species of reptiles and amphibians, more than half of which are threatened or endangered. There’s a good chance of spotting sloths, monkeys, and many species of birds in a trip through the forest, especially in the early morning.

The Laguna de Bastimentos, near the north coast midway across the island, is home to freshwater turtles, caimans, and crocodiles. Do not attempt a hike through the forest without a guide; you will get lost.

Playa Larga, which is part of the park, is an important sea-turtle nesting area, attracting four species of endangered turtles from about April or May through September.

Admission to the park is US$10 per person. Even those just snorkeling or diving in the waters around the Cayos Zapatillas must pay this fee. Ask the tour operator if the fee is included in the price of the tour. There are plans in the works to expand this beautiful park.