"Coz is Coz for things down there, not up here,” Scuba Du’s Aldo Mejia says as we relax along a pretty stretch of Cozumel’s malecon, a seafront promenade that parallels busy, bustling Avenue Rafael E. Melgar, where margaritas and cervezas flow with the tides. He points toward the 12-mile channel between Coz and Mexico’s Yucatan peninsula, home to some of the best diving on the planet. “The visibility is amazing.”

Grounded for a day by wind and rain, I’m dying to find out. We finally head over Coz’s famous wall with guides from Scuba Club Cozumel at Palancar Gardens, part of the 3-mile Palancar reef system, a favorite of local divemasters. “Garden” isn’t exactly the right word for these monumental, mazelike structures with tunnels, swim-throughs and wide, sandy passages that make it easy to explore high and low.

We spiral down from 25 feet to about 80 on a gentle magic-carpet ride — Coz currents, commonly around 2 knots, can reach a ripping 6 knots — gliding through formations stuff ed with gigantic sponges, elephant ears glowing a neon orange, and so many rope sponges that it gives new meaning to the word “festooned,” strung like crepe paper at a high school dance. Sensory overload sets in in room-size domes under every overhang, plastered with more sponges everywhere you look.

Beginning our meandering ascent, we spot every sort of reef fish at a multitude of cleaning stations as we follow our divemaster in and out, here and there, over coral hills and sandy dales, where huge grouper patrol the pathways, each new turn revealing something beautiful or fun, or both.

Eventually the formations drop away as we start a long, slow safety stop looking down on the world’s biggest, friskiest free-ranging lobsters skittering about, so large they’re almost grotesque. Hilariously homely splendid toadfish — endemic to Coz — also begin to show themselves in large numbers.

Our second dive, at nearby Tormentos Reef, is entirely different in character — who knew Cozumel had muck diving? Along a sandy bottom at about 55 feet, we find dragonets, snapping shrimp, pipe seahorses, sailfin blennies in courtship display, and more pouty-faced toadfish than we can count, rounding out a morning that’s splendid indeed.

WHAT TO DO TOPSIDE

DRINK Just mention the “Bob Marley bar” and anyone can point you to this laid-back beach bar where you’re guaranteed to make a friend.

SLEEP Luxe is the word at gorgeous InterContinental Presidente Cozumel. From its gourmet restaurants to seaside pool to stunning rooms, you’ll be treated like royalty.

EAT A turn-of-the century house turned courtyard restaurant, Pancho’s Backyard serves classic Mexican cuisine, and drinks in goblets as big as your head; the cream of cilantro soup is a revelation.

DIVE OPERATORS

SCUBA DU Headquartered at the InterContinental Presidente Cozumel for more than 30 years, Scuba Du also has dive shops at Hotel B and Casa Milena. Smaller boats, personalized service, and a warm and friendly staff add up to a top shelf experience above and below.

SCUBA CLUB COZUMEL Truly a diver’s dive resort, the grand old señora of Cozumel diving — founded in 1976, with staff who will remember you and welcome you back — oozes local charm, and houses one of the best dive operations on the island, as its massive numbers of repeat guests will attest.

PRO DIVE INTERNATIONAL Two of Pro Dive International’s three Cozumel dive shops are on the island’s southwest shore — at spectacular Occidental Grand and diver-friendly sister resort Occidental Allegro — a location with great beaches and as close to Cozumel’s best diving as you can get.

DIVE GUIDE

DIVE CONDITIONS
From 75 degrees in winter to 85 in summer; strong currents are a signature; drift diving is the norm.

WHAT TO WEAR
Many divers are fine in a bathing suit or boardshorts; for repetitive diving, a 3 to 5 mm wetsuit should suffice.

TRAVEL TIP
Fly in to Cancun, catch the bus to Playa del Carmen, and take a ferry to Coz. Rent a car at the ferry terminal; Coz is an easy place for drivers to navigate, and a car allows you to explore the island.

WHEN TO GO
Year-round; trip insurance is a good idea during hurricane season.

TO LEARN MORE

To learn more about diving and visiting Cozumel, go to cozumel.travel.