Best things to do in December in Cancun?

I'd recommend snooba diving at Xcaret, it was a great experience for both of us, even though we had never snorkeled before.

Cancun's warm waters and smaller crowds in December make it an ideal time for snorkeling. Instead of joining a big catamaran tour, consider visiting Puerto Morelos, a charming town about 30 minutes south of Cancun. From the town pier, you can board a small, licensed boat for a roughly two-hour trip to the reef, where the park entrance fee is paid upon arrival. Another easy day trip option is Isla Mujeres, accessible by ferry from Puerto Juárez. Once there, you can rent a golf cart and explore the island, visiting Playa Norte in the morning and Punta Sur before the crowds arrive. Afterward, grab lunch at a restaurant on the north end of the island. In Cancun itself, the Museo Maya de Cancún in the Hotel Zone offers a peaceful couple of hours, with a small ruin site located behind the museum.

To make the most of your day trip to Isla Mujeres, consider renting a golf cart to navigate the island efficiently, especially since it can get quite hot. Start your day by heading straight to Playa Norte, where you can park your golf cart nearby and walk to the beach club. Access to the club costs around $30 for two people, but it's well worth it, as you can stay as long as you like and enjoy the beach cabanas, chairs, pools, and other amenities. The beach club was a lot of fun, and you can return whenever you want.