Walk Fifth Avenue (without the tourist traps)
Go early morning or late evening to avoid the crowds and the aggressive timeshare pitches.
Swim in a cenote
Several cenotes are a short drive away and offer a completely different experience from the beach.
Take the ferry to Cozumel
A quick day trip for snorkeling and diving on some of the best reefs in the region.
Visit a local market
Skip the souvenir shops and visit a local market for authentic food and crafts.
Relax at a beach club
Many beach clubs offer day passes that include loungers and a food/drink credit.