Diving the Bat Islands (Islas Murciélago)

The islands

The Bat Islands, Islas Murciélago in Spanish, are a cluster of steep, rocky islands off the Santa Elena Peninsula in Costa Rica's far northwest, close to the Nicaraguan border. They're part of Santa Rosa National Park's marine sector, inside the Área de Conservación Guanacaste, a protected area that also covers dry forest, beaches and volcanoes on the mainland.

The waters here are exposed and full of life. The conservation area points to schools of jacks, mantas, whales and dolphins, depending on the season. For divers, though, one animal stands out.

Bull sharks at the Big Scare

The Bat Islands are known above all for bull sharks, and the conservation area names the bull shark as the species that draws the most attention from divers. The encounters happen at a site called the Big Scare (El Gran Susto in Spanish) at Isla San Pedrillo, one of the outer islands. Dive shops describe sharks of around 2 meters cruising along the rocky bottom, often at depths past 30 meters.

There's more than sharks. Giant manta rays pass through, schools of devil rays can be huge, and big schools of fish swirl around the rocks. Humpback whales and dolphins are seen on the crossing in season.

Who can go

This is advanced diving. Rocket Frog Divers, one of the shops that runs the trip, says it isn't for new divers, because currents can be strong and dives can go past 30 meters (100 feet), with sharp thermoclines and visibility that can change within a single dive. Expect a dive shop to ask for your certification level, your logbook and recent experience. If you're newly certified, dive the Catalina Islands or the local Papagayo sites first.

The park's rules

Because the islands are inside a national park, the Área de Conservación Guanacaste sets the rules, and your dive shop arranges the paperwork:

• Where you can dive. Recreational diving is allowed only at 3 sites: the Big Scare at Isla San Pedrillo, Los Arcos at Cabo Santa Elena, and Bajo Negro.
• Booking. Boats must register each visit in advance through the conservation area's marine reservation form, listing the date, the visitors, the crew and the boat. Entry is limited by the capacity set for each activity.
• Fees. Admission must be paid before entering the marine sector.
• Anchoring. Boats may anchor only off the ranger and research station on Isla San José.
• Hands off. Taking animals, plants or anything else from the park is banned. Fishing isn't part of a visit here; this is a protected area, and anglers should fish outside it.
• No landings. The islands' trails have been closed to visitors since 2022 because of damage to the ecosystem, including turtle nesting beaches. Diving and snorkeling continue.

When to go

The Bat Islands are at the mercy of the wind. In the dry season, roughly December to April, strong Papagayo winds blow across the gulf and can make the crossing rough or impossible. Rocket Frog says visibility is usually best from May to November, when the winds ease and the water is a little warmer. Even then, shops check sea conditions every morning, and trips are often confirmed only the day before.

Getting there

Most trips leave from Playas del Coco, with some from Playa Hermosa and the Papagayo Peninsula. The run is about 30 miles across the Gulf of Papagayo, and how long it takes depends on the boat and the sea. A day usually includes 2 dives. Rocket Frog Divers in Playas del Coco is one shop that runs it, and our Playas del Coco guide covers the town.

Learn more

Our sister site scuba.cr has more on diving the Bat Islands.