San Andrés is a Caribbean island belonging to Colombia, sitting closer to Nicaragua than to the Colombian mainland. The sea around the island is famous for its "seven colours" — bands of turquoise, aquamarine, and deep blue created by the varying depth of the coral reef — and the snorkelling and diving are outstanding.
The island has a distinct Raizal culture, descended from English-speaking Afro-Caribbean settlers, and you will hear Creole English alongside Spanish in the streets. The main town along the north shore is busy and commercial, full of duty-free shops catering to Colombian tourists, but the quieter east coast and the southern tip have beautiful beaches and a more relaxed feel. A short boat ride takes you to Johnny Cay, a tiny coral islet with white sand and coconut palms, or to the Acuario, a shallow sandbar where you can wade among tropical fish.
For a quieter alternative, take the catamaran to nearby Providencia, a much smaller and less developed island with some of the best diving in the western Caribbean.