Many cenotes offer incredible diving opportunitiees. Consider Cenote Zapote to see giant rock formations called "Hells Bells". The Pit is the deepest sinkhole in the Yucatan at 391 feet! Other popular cenotes for diving include Dos Ojos, Maravilla, Angelita and Carwash, which takes on a redish color and is filled with trees, plants, fish and turtles.
The majority of cenotes in the Yucatan have solid infrastructure to help you access them and many even offer or require life jackets. Cenote visits are a safe activity as long as you use good judgement (we're looking at you backflip-off-a-cliff-guy) and follow the local guidance.