Costa Rica’s Bat Islands are an ecological treasure not to be missed. An important part of Santa Rosa National Park, the Isla Murcilago, as the area is called, is located in northern Guanacaste off Santa Elena Peninsula. With old hacienda buildings on shore, plus incredible rock formations above and below the water, the area is fascinating not only for its abundant marine life, but for its history and geology. In addition, the Bat Islands are the site of Naranjo and Nancite, which are nesting habitats for sea turtles, including the Pacific Ridley Sea Turtle, which is a vulnerable species.
Diving Conditions
Between December and April, which is the peak dry season, water temperature is normally 70 degrees or so, while it is usually between 76-80 degrees between May and December. There are thermoclines in the 80-100 foot zone, as well as currents and upwellings which can cause the water temperature to change with unpredictable rapidity. Visibility is normally between 30 and 100 feet, depending on multiple factors, such as season, tide, and currents. Interestingly, outside air temperature is normally between 85-90 degrees year round, and humidity tends to be low.
Marine Life
Best known for the abundance and diversity of marine life large and small, the Bat Islands have picturesque inlets with rock formations that date back to the cretaceous period, as well as magnificent pinnacles, all covered in a splendid tapestry of colorful growth and crawling with a variety of invertebrates, crustaceans, and other creatures. With schools of fish numbering in the thousands, including countless reef fish in every color of the rainbow, it is possible to find both Tropical Pacific varieties as well as Caribbean species as you explore. In addition, the rocks shelter a whole host of moray eels, including zebra morays, green and jeweled morays, snowflake morays, golden morays, and white mouth morays.
Perhaps most exciting of all though, are the many larger species which can be found with regularity. Whale sharks, giant manta rays, eagle rays, bull sharks and several types of reef sharks, giant groupers, and turtles are those most commonly encountered.
The Big Scare
While there are diving opportunities all around the islands, the site known as The Big Scare features a group of rocks which break the surface. The best place to encounter bull sharks, sailfish, marlin, and schooling jack, pompano, spadefish, and others, it can be a bit murky at times, particularly as you reach maximum depth of about 90 feet. While it is possible to see some of the larger animals at depths between as shallow as 20 and 30 feet from time to time, the greatest concentration is in deeper water.
In addition, divers regularly see pilot whales and orcas, pods of spinner dolphins, and other cetaceans, particularly while drifting in open water during safety stops.
The Refuge
Between the islands is the area known as the refuge, which is where you will normally spend surface intervals, and which is also a great spot for snorkeling and relaxing encounters with schools of cownose rays, wahoo, and passing manta rays. Here, maximum depth is 30 feet, and visibility is usually better than 100 feet.
You will need an Advanced Open Water certificate or equivalent to really enjoy diving Bat Islands, and local dive operators can usually accommodate singles and couples with ease, so long as you sign up as soon as you arrive in Costa Rica. Of course, if you want to ensure a spot for a particular date, particularly during high season, it is best to book in advance. Remember your camera on this trip – what you see will surely amaze you!