The rather remote village of Miguel Colorado, 70km south of Champotón, has two large scenic cenotes (limestone sinkholes) with a spiffy new ecocenter and a private nature reserve. Full admission includes kayak rental and a couple of very high zip-lines that go over one of cenotes. You can hike (M$80) along hilly, rocky trails to each cenote, keeping an eye out for spider and howler monkeys.
It's possible to visit a bat cave in the area and a lake called Laguna de Mokú (home to crocodiles), but you'll need a guide (M$50 extra for each).
To get to the cenotes, drive 60km south of Champotón on Hwy 261, then take a 10km side road to the village of Miguel Colorado. Turn left at the village and go 3km more.