The entire hotel zone is really one long beach. You will have a hard
time finding a hotel that does not have a good beachfront,
whether it is a 2-star hotel or 5-star. And if the beach
in front of your hotel is not to your liking, you can walk over to the
next hotel's beach and swim there, use their chairs, play volleyball,
go parasailing, and so on. The beach is all public property, except
around the Club Med.
Ocean versus Lagoon
Although the Cancun coast includes both an "ocean side" and a "lagoon side", by far the majority of the hotels front onto the ocean. There isn't any beach to speak of on the lagoon side. Swimming and tanning takes place on the ocean side, and jet-skis, kayaks, and other rentals are featured on the lagoon side.
What About the Hot, Burning Sands?
Unlike beaches in Florida and elsewhere, the beaches in Cancun are made of crushed coral rather than crushed rock. The coral stays cool even on the hottest days; you don't need to worry about burning your feet. You can go down to the beach barefoot if you like.
The only problem with the sand is that it is very clingy. When you leave the beach, be sure to wash the sand off your feet, legs, back, and butt. Otherwise it will come off in your hotel room and possibly your bed.
The parasailing that I saw being offered to anyone walking by on the beach was opposite the Fiesta Americana hotel, around the middle of the hotel zone and just 1-2 hotels up from the Omni where I stayed. The cost is $35 US. There is also parasailing at the Aquaworld marina, using a 2-seater.
There is a volleyball net in the same area, another much farther up near the Casa Maya, and I'm sure many others. I was disappointed not to see anyone playing. The energy level of the real people in Cancun is nowhere near as high as in the photos of the tourist brochures.
The Pool or the Beach?
In 2 weeks in Cancun, I didn't see anyone actually swimming in the pools. Just a few people wading or soaking. The beach is really the more popular place for recreational activities like swimming and tanning. Also, the pools tend to have music playing over loudspeakers all the time. Be warned that this music sometimes includes the Macarena!
Because the sun rises in the east, facing the beach, it is better to tan in the morning and at mid-day than in the afternoons. I found the shadows starting to intrude on the lounge chairs by about 3 PM.
The Cancun shops feature suntan lotions with higher protection factors than you can probably find at home. Prices start around $10 US. There are also various bronzing lotions.
All of the swimming I saw was on the ocean side, with the lagoon area more for boat rentals and guided tours. The Atlantic surf is pretty high and most of the swimming consisted of bobbing in the waves.
Depending on the wave and tide conditions, each section of the beach is marked with a flag indicating whether it is safe to swim there:
The best snorkeling area off the beach is the public area near the Westin Regina, down in the southern tip of the hotel zone. Most of the other places (Isla Mujeres, Cozumel, or some of the lagoon tours) require a substantial trip and signing up for a tour.
For more on snorkeling, see Tours.