Isla Mujeres

Well, Mexico City being in the middle of the country, I would try Isla Mujeres or around Campeche.

The cliffs and water there are stunning and the ocean color changes between deep blue and bright turquoise depending on where you are.

Took the ferry from Cancún in the morning and returned in the evening. Rented a golf cart and drove around the island from north to south and back. The water there is unbelievably blue and the island is small enough that exploring by golf cart is really fun.

For snorkeling, look at Cozumel or Isla Mujeres!

for the no-car, walkable, snorkel-off-the-beach combo specifically, the sleeper nobody's mentioned is isla mujeres - it's a golf-cart island, calm on the leeward side, easy to get around on foot, and you can pair a casual base with a nicer spa day.

I would recommend doing a trip over to Isla Mujeres instead of going down to Xcaret. Purely because of your limited time there.

Isla Mujeres has none of that over there. Practically clear turquoise waters..

Take the ferry to Isla Mujeres one day. Rent a golf cart, go to Punta Sur. Better than any excursion you'll book through the resort.

folks usually take a day trip to Isla Mujeres