PROTRUDING LIKE A GIANT THUMB from the east coast of Mexico, the Yucatan peninsula is a huge landmass that divides the Gulf of Mexico from the Caribbean Sea.
The most well-established resort area is the purpose-built enclave of Cancun on its northern tip.
This fascinating peninsula is mostly low-lying, covered by dense jungle and swamps criss-crossed with rivers, and scattered about with the intriguing ruins of the great Mayan civilisation.
As well as being rich in history, the Yucatan is also blessed with superb beaches lapped by the crystal-clear waters of the western Caribbean, sophisticated resorts and some of the best diving and snorkelling in the Caribbean.
Offshore from Cancun are three islands, the largest of which is the world-famous diving destination of Cozumel. Her sister-islands are Isla Mujeres and Isla Contoy, which lie to the north.
These three islands in the western reaches of the nutrient-rich Gulf Stream are formed in part by the largest barrier reef in the northern hemisphere, which stretches north from Honduras, Guatemala and Belize.
Above sea level, the land is rather uninspiring and the coral platform of Cozumel is all that is left of the tip of an ancient volcano. The immediate surprise is the exceptional quality of the diving down the coastline, where, in addition to the virgin reefs offshore, there is also the added bonus of exciting and challenging cave-diving in the spectacular cenotes, or limestone sink-holes. You will very quickly appreciate that the diving to be found here is world-class.
Both Cancun and the coastline to the south suffer from the periodic winter storms that occur in the southern Caribbean, resulting in a long low swell that makes boat trips and times between dives rather uncomfortable.
This is where diving in the cenotes really comes into its own.

Cozumel is Mexico’s largest Caribbean island at 29 miles long by nine miles wide. The Island of Swallows, as it was once known, is ranked by the American diving press in the top five destinations for Caribbean diving, with good consistent water clarity of over 30m on average. This also means that it is one of the busiest.
Although the onboard divemasters will plan your dive and dive time, it is pretty haphazard and they always lean towards the most inexperienced diver, cutting down your own bottom time. Therefore it is very important to do your own pre-dive planning.
Palancar Reef is one of those names that is always mentioned when divers talk of Cozumel.
The reef is simply massive, and of the 150 dive sites registered around Cozumel, Palancar has four.
Stretching over three miles, this largely pristine reef offers an amazing diversity of marine life and coral formations to suit all tastes and levels of diving expertise.
As all of your diving will be drift-diving, there is little diver intrusion on the reefs, which are well fed from the nutrient-rich waters of the Gulf Stream.
Further to the north is the Santa Rosa Wall, and this is perhaps one of the favourite dives in Cozumel.
In fact this reef can easily be split up into three totally separate dives, giving much better opportunities to see its bounties. As in any exposed area, the southernmost section is low-lying and scoured by currents.
The middle section has some very large tunnels, which completely cut through the reef crest, and the most northerly area of reef has tunnels, caves, overhangs and very steep sections of wall running to near-vertical conditions.

South from Cancun on the Highway Mex 307 past Puerto Aventuras towards Akumal and Tulum you will come across signposts for cenote diving. More than 250 million years ago, the Central American Continent was under water, and during the last Ice Age the sea level dropped and ultimately left a shallow raised plateau of soft porous limestone.
This bedrock is susceptible to erosion, and severe tropical rainstorms over the centuries have created huge underground caverns and wells.
A cenote is created when the roof of one of these vast caverns collapses.
In the south of the country, near Chetumal, is Cenote Azul, the deepest cenote in the world at over 100m.
There is a charge for all cenote diving as it takes place on private land – some have crude changing huts or simple platforms at the water’s edge.
Although Nohoch Nah Chich is the most famous, other sites such as Ponderosa, Dos Ojos and Car Wash are easily accessible, but for sheer scale El Grande Cenote is absolutely superb.
This huge circular hole is a collapsed cavern over 60m across with the centre completely filled in. Entry is 6m down a set of rickety steps to the edge of the cenote, where you will dive into the labyrinth of inter-connecting caverns, only lit occasionally by shafts of sunlight coming through other cenote entrances.
The entrance to the cenote has a carpet of lily pads.
Gauging visibility is always difficult, but when you are more than 60m into the cavern and you can see someone snorkelling at the entrance, you know it is good! There are stalactites, stalagmites, flow stone and many other fabulous formations.

Tropical maritime, with nice warm winds, but also very high humidity. June to November is hurricane season, with most of the rain also falling in that period. In summer, temperatures can rise to 40°C.

November to March is best for the freshwater dive sites, as there is always a high algae bloom in the summer, rendering visibility like “pea soup”! May to September is considered best for the Cozumel reefs, but is also hurricane season.

Cancun and Cozumel are directly accessible from a number of airport hubs in the USA. Cancun is a great base to travel down the Mayan Riviera to the cenotes and it is easy to catch one of the regular ferries to Cozumel to save flying.

Does not vary much and averages around 28°C. Visibility is usually around 18-30m and considerably more in the cenotes.

Fish life is exceptionally varied and the largest concentrations are found surprisingly in Cancun Bay. There are some of the largest schools of snapper and grunt I have seen anywhere in the Caribbean. There are one or two interesting fish to look out for, or should I say “listen out for”. Toadfish in particular are worth mentioning. The name comes from the curious loud “croaking”, which you can hear quite clearly under water. They live under a hollow of coral which seems to magnify the sound and it can carry quite far under water. It certainly helps you locate them, as they are active only at night.

Averages around 25m but most diving will be done as a twin-tank dive with a deep dive to 30m first, followed an hour later by a dive to around 18m. Afternoon dives and night dives are generally no deeper than 12m.

Virtually all of the diving in Cozumel is drift-diving, so divers must be very aware of their buoyancy at all times. Always take extra sunscreen to plaster on after the dive, as boat trips can take as long as one hour to the more distant dive-sites. You must wear a protective suit and hood at all times in the cenotes, as the freshwater temperature is about 10° cooler than the sea and the freshwater mollies and tetras can bite quite painfully.

Lawson Wood’s comprehensive illustrated reference book covers a huge variety of wrecks, marine habitats and aquatic species in the Caribbean, Red Sea, Indian Ocean, Indo-Pacific and Pacific Ocean.
The descriptions detail the type of dive to be experienced as well as what you can expect to see. Each dive site featured can be located via a detailed regional site map, and a travel advisory is also included.
Lawson Wood has authored and co-authored more than 45 books, mainly on our underwater world. He is a founding member of the Marine Conservation Society, founder of the first Marine Reserve at St Abbs in Scotland, and was the first person to be a Fellow of both the Royal Photographic Society and the British Institute of Professional Photographers solely for underwater photography.
The 260 x 215mm hardback book is published by John Beaufoy Books in September, ISBN 9781906780234. Its 208 pages include 300 colour photographs and 80 maps. Price is £24.95.