Dos Ojos is a cenote (or actually two, as the name means "two eyes"). Cenotes are sinkholes created when the roof of a cave system falls in, exposing the water beneath, so many cenotes provide access to diveable cave systems (and Dos Ojos does).
Many companies offer cavern tours for open water divers. If you have enough diving experience to have good buoyancy control and reasonable horizontal trim, and you've dived enough to know you stay calm in the face of minor problems in the water, then you can get a taste of how beautiful the caves are. Look for a dive operator who follows the voluntary rules for guides: Full cave, open water instructors, diving in full cave gear, with no more than 4 clients at a time.
Many companies offer cavern tours for open water divers. If you have enough diving experience to have good buoyancy control and reasonable horizontal trim, and you've dived enough to know you stay calm in the face of minor problems in the water, then you can get a taste of how beautiful the caves are. Look for a dive operator who follows the voluntary rules for guides: Full cave, open water instructors, diving in full cave gear, with no more than 4 clients at a time.