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Bull shark encounters at the Bat Islands are conducted under controlled conditions with experienced guides. The sharks are typically resting on the bottom at deeper sections of the pinnacles between 20 and 30 metres during the cooler water months. Divers maintain a respectful distance and observe from stable positions on the rocks. The sharks at this site are not baited or fed, and they are engaged in natural resting behaviour during the thermocline-driven cool water period. Serious incidents involving divers have not been recorded at this site, but the advanced certification requirement reflects the challenging conditions rather than shark aggression.

The Bat Islands sit in a zone affected by seasonal upwelling and thermocline dynamics in the eastern Pacific. During the rainy season from May through November, nutrient-rich cold water wells up from the deep, dropping temperatures as low as 18 degrees Celsius at depth. This cold, nutrient-dense water attracts plankton feeders like manta rays and whale sharks, as well as bull sharks that favour cooler temperatures. During the dry season, warmer surface water dominates and visibility improves but the megafauna moves to deeper water. The temperature difference between surface and bottom can exceed 8 degrees on a single dive.

The boat ride from Playas del Coco to the Bat Islands takes approximately one and a half to two hours each way, depending on sea conditions. The islands are located within the Santa Rosa National Park offshore sector, and access is regulated by park authorities. Dive operators typically depart very early in the morning, around 6am, to maximise time at the islands and return by early afternoon. Some operators offer two-day trips with overnight stays on the boat. The journey crosses open Pacific water and can be rough, particularly during the rainy season when seas are more active.