Isla Cozumel
Isla Cozumel is an island just off the coast between Cancun and Tulum. It's mostly undeveloped, but it's famous for its cruise ship port and its amazing reefs, perfect for diving. You can explore the Mesoamerican Reef or check out Chankanaab, an eco park with a beautiful lagoon.
The city center caters mainly to tourists from the cruise ships, with lots of expensive shops, restaurants, and some bars. Not much to see there, honestly.
If you're looking for a great place to stay, I highly recommend La Casona Art & Recycling hostel. They even have a little Scuba School with instructors from all over the world! The whole vibe of the place is super chill, with plenty of spaces to hang out and meet people. Plus, breakfast is included, and the host is really friendly. They've got a kitchen too, so feel free to cook up whatever you want.
For a fun night out, head to Green House for some beers and a game of pool!
Getting to the island takes about 40-60 minutes from the mainland and costs around 135 Pesos (about 5 euros). There are plenty of safe parking spots around the terminal, so no need to worry about that.