The crystal-clear turquoise lagoon of the Riviera Maya: a genuine paradise on earth
My suggestion:
Go there!!! It's even accessible to those travelling on very limited budgets: some of the little hotels offer areas in their gardens where you can pitch your tent.
My review
Bacalar's lagoon has everything you could possibly hope to imagine when contemplating a little tour of the Caribbean: Incredible panoramic views at sunrise and sunset; starry night skies with the Milky Way clearly visible; peaceful bathing in warm, translucent water; enjoyable aquatic activities; fish in all kinds of sauces, etc., and all far from the consumerist debauchery found at other places further up the peninsula.