The Tecoh caves (10 a.m.–5 p.m. Mon.–Fri., 8 a.m.–5 p.m. Sat.–Sun., US$3) is something of a mixed bag: A 1.5-hour tour leads you past a dozen crystalline underground cenotes, but the walls and limestone formations are marred with the spray-painted messages of local kids and couples.
The payoff is a 50-meter (164-foot) crawl to the last and largest cenote, which has beams of sunlight entering from two holes in the roof and makes for a refreshing swim.