Bat Islands

The Bat Islands (Islas Murciélagos) are a group of small islands sitting at the outermost western tip of Santa Rosa National Park, roughly 30 miles north-west of Playa Ocotal in mainland Costa Rica. Access is by boat, with journey times ranging from about 40 minutes to two hours depending on the departure point. These are non-anchored, deep dives across multiple rocky sites, with maximum depths varying from 18 m (60 ft) to around 32 m (105 ft), and the terrain is characterised by surge, strong currents, and rougher surface conditions than are typical of the region.

The standout marine life draw is bull sharks, regularly encountered at over 3.5 m (12 ft) in length. At Black Rock, an isolated pinnacle within the group, squadrons of eagle rays, schools of horse-eyed jacks, cow-nosed rays, snapper, spadefish, grunts, and gaff-topsail pompano are common. Manta rays, whale sharks, and sailfish appear occasionally, and during January and July migrating orcas and humpback whales pass through the area.

Visibility averages 12–18 m (40–60 ft) and can range from around 9 m (30 ft) to 30 m (100 ft) across the year, depending on tides and currents. Upwelling is a feature of the site and can produce thermoclines that drop water temperature by several degrees within a short vertical distance; overall water temperatures range from 21–27°C (70–80°F). Conditions are exposed year-round, with occasional swell adding to surface difficulty.