Worlds longest Under water Cave Systems is in the Yucatan From Rivergirls original post in Cancun Info: http://www.cancuncare.com/forum/viewtopic.php?t=30045 I thought this would also be a good place for this hope you don't mind Rivergirl!
Re: Worlds longest Under water Cave Systems is in the Yucata Between Quintana Roo and Yucatan there is the largest cave, cavern system in the world, it is a Guinness record and has been for a while, lately there has been an amazing discovery of yet another larger system. Diving the caverns is a wonderful experience but sometimes confused with cave diving wich many divers do not know there is a big difference, for cave diving special training and equipment are needed, for cavern diving the Open Water Certification by any recognized agency is enough, it is consider a cavern because even at some dark spots, the sunlight still is seen, a cave is total darkness. It is awesome to dive caverns and while in cancun it is great to take the time to do it. For more info on cavern click on www.mantadivers.com and lets go diving.