This beach is only accessible by boat or by paying the entry fee to get into the Tulúm ruins.
Once inside and walking around the ruins, you are sure to see people walking down the long set of stairs to go in for a swim. When we were there at 10am, it was relatively empty but by 11am it was packed with day trippers from Cancun and Playa del Carmen.
Definitely worth wearing your trunks if you are making it to the ruins and going in for a dip as it can get pretty hot there at mid-day.
Close your eyes and imagine what it would have felt like in the days of the Maya... but you might need headphones to block out the background noise.