1. The Great Blue Hole, Belize
Experienced divers can explore the Blue Hole, a perfectly circular cave plunging vertically into the sea bed. Seen from above this cavernous sinkhole is a dark disk in a bright aquamarine ocean, seemingly swallowing the light into its underwater reaches. There are extraordinary underwater stalactites to be seen on the sheer walls, which descend to a depth of 125m, while a number of shark species roam around inside.
Go Caribbean diving in Belize
2. Fernando de Noronha, Brazil
The only populated island in a protected volcanic archipelago way out in the Atlantic Ocean, Fernando de Noronha is almost off the map. But those who go there (and numbers are restricted), especially divers and surfers, are well rewarded. Craggy cliffs jacketed in close garrigue-like vegetation (the original forests were destroyed) close in on gorgeous little bays of sugary sand, and the waters here, warm year-round, are sapphire-clear. Much of the area is designated a marine park, for good reason: sharks, dolphins, turtles and stingrays and a multitude of fish species thrive here.
Go scuba diving in Brazil
Active Brazil: Remote Bahia and Fernando de Noronha (15 days from £2,185pp)
3. Galápagos Islands, Ecuador
The Galápagos Islands shelter some of the world's best dive sites, offering the chance to gape at an astounding aquatic panorama where penguins dart through equatorial waters and vast shoals of hammerheads patrol the ocean.The convergence of cold currents from Antarctica and warm tropical waters has created microclimates which sustain an incredible spectrum of marine species, many of which would not normally be neighbours.
Diving in the Galápagos
4. Yucatán Peninsula's cenotes, Mexico
How many of us can say we have dived in one of the world’s largest freshwater cave systems? This truly is an experience like no other. The Yucatán Peninsula is a huge porous limestone shelf where fresh water flows into underground river and cave systems. Parts of the shelf have collapsed over thousands of years creating sinkholes or cenotes. These underwater caves and caverns popular among divers today were believed by the ancient Mayans to be entrances to the mystical underworld. Each cenote is different - some are completely underground, others semi-underground - in many the roof allows sunlight to penetrate, creating a magical feeling and intense aquamarine colour.
Explore freshwater cenotes