The Rosario Islands

The Rosarios are a scatter of low coral islands and cays off the Bolivar coast, protected together with the San Bernardo group as a national park. The water is clearer than anything on the mainland shore, the reefs still hold a reasonable range of hard and soft corals, and Isla Grande, the largest island, has an inland lagoon where plankton light up on a moonless night swim. Day tours run out from Cartagena every morning and back in the afternoon; staying a night or two on one of the islands is a different experience entirely, because the boats leave in the late afternoon and the place empties out.

What you actually see

• The reefs - snorkelling and diving over hard and soft coral in clear water.
• Isla Grande - the largest island, with mangrove channels and walking paths.
• The bioluminescent lagoon - plankton that glow when disturbed on dark nights.
• The sand cays - small low islands with shallow turquoise water around them.

When to go

December to April is the driest stretch and the sea is calmest, which matters on an open boat crossing. Leave on the first boats of the morning to reach the snorkelling spots before the fleet arrives. The bioluminescence needs a moonless night, so check the lunar calendar if that is the reason you are going.

Honest expectations

Day tours are a conveyor belt: a fast wet boat, a rushed snorkel stop, a beach club lunch and constant selling of massages, drinks and further boat trips. Reef condition varies and some areas are visibly bleached or broken. Prices at the island beach clubs are far above mainland rates, and the park fee is collected separately from the tour price.

Nearby

Cartagena, the Baru peninsula and the San Bernardo islands lie along the same coast.