The Rosario Islands have 28 known diving sites, ranging from shallow coral gardens ideal for snorkelling to deeper walls and reef structures for experienced divers. Visibility on the best days exceeds 20 metres. The waters hold grouper, barracuda, moray eels, sea turtles, and a range of reef fish; sightings of eagle rays are not uncommon.
Most day-tour boats from Cartagena stop at two or three snorkelling spots, which is enough to get a good sense of the reef. Serious divers will want to book with one of the dive operators that can take them to the less-visited sites in the southern part of the archipelago.
The reefs here are not in perfect condition — warming waters and past damage have taken their toll — but they remain among the best accessible from the Colombian coast, and the marine park protections have helped.