Crab Cay is a small rocky islet within the Old Providence McBean Lagoon National Park, widely regarded as the best snorkelling spot on Providencia. The shallow coral gardens immediately offshore are rich with parrotfish, angelfish, sergeant majors, and the occasional nurse shark resting on the sandy bottom. The reef here is in significantly better condition than most Caribbean reefs, benefiting from the island's low visitor numbers and the protection of the national park.
Boat taxis from town can take you out to the cay, or you can arrange snorkelling and diving trips from operators based in Santa Isabel or Aguadulce. The water is clearest in the morning before the afternoon chop picks up. There is a small visitor center run by the park. Bring your own snorkel gear or rent from operators in town — selection is limited.