What should I pack for Cozumel?

Cozumel enforces biodegradable-only sunscreen inside Arrecifes de Cozumel National Park, established in 1996. The rule has teeth. Guards at Chankanaab and Palancar access points check bottles and take anything non-compliant. Pack reef-safe SPF 50 from home. The local options at Mega supermarket on Avenida Rafael Melgar run 180-250 MXN, roughly double US retail for the same brands. A UPF 50+ rash guard does more than lotion alone once you're in the water. The Caribbean off Cozumel holds at 28-29°C year-round, warm enough to skip a wetsuit but deceptive. Three hours of drift snorkeling over the wall at Colombia reef will cook an uncovered back. Salt water strips lotion faster than a pool. Mind you, the rash guard earns its place twice on boat day, when bow spray soaks everything from the waist up before you've reached the dive site.

The ironshore limestone on Cozumel's windward coast will slice bare feet before you feel it. Chen Rio has a sandy entry at the waterline, but the path down crosses rubble sharp enough to cut through foam sandals. Bring hard-sole water shoes. Not the mesh 'aqua socks' that fold flat in a suitcase. You need rubber thick enough for jagged coral rock. San Gervasio's Maya ruins sit inland on compacted gravel and exposed root, fine for trail sandals or closed walking shoes. Downtown San Miguel's waterfront malecón is smooth tile. Any casual shoe works there. Three pairs covers the island. One water shoe for reefs and east-coast coves. One trail sandal for the ruins and the scrubby paths at Punta Sur. One flat or loafer for dinner at La Cocay on Calle 5 or Buccanos at Night near the north hotel zone.

Cotton is a mistake when the heat index sits near 39°C. It sticks to your chest by 10 AM and stays damp until you change. Pack 3-4 quick-dry synthetic shirts and 2 pairs of performance shorts. Add one light long-sleeve for the Ultramar ferry back from Playa del Carmen. The evening wind off the Cozumel Channel drops felt temperature by 5-6 degrees, and the AC inside the terminal raises goosebumps on sunburned arms. Cozumel has no dress-code-strict heritage sites on the tourist circuit. San Gervasio requires nothing beyond shoes and a shirt. You can do the whole island in shorts and sandals, which is unusual for a Mexican destination with heritage sites. One nicer outfit handles dinner at Kondesa on Calle 5 or the rooftop at 1945 on the malecón. Neither demands formalwear, but board shorts stand out after 7 PM.

Snorkel sets at the dive shops near Punta Langosta rent for 150-200 MXN per day. A 3-day rental runs close to the cost of a mid-range set from home, so the math turns on how often you snorkel in a year. If you bring your own, pack mask and snorkel. Leave the fins. Fins eat suitcase space, and the rental pairs handle the gentle drift currents at Palancar and Colombia reefs without trouble. A 15-20L dry bag earns its weight on every boat excursion. The pangas that run reef trips take salt spray over the gunwale, and your phone needs somewhere sealed. Leave the umbrella at home. Wet-season squalls pass in 15-20 minutes, and Chedraui on Avenida 30 sells them for 90 MXN if you get caught. Same logic for bug spray. Off! at any Oxxo runs about 45 MXN, and the island's steady sea breeze keeps mosquitoes tolerable everywhere except the still, muggy mangrove edges near Punta Sur after 4 PM.