Divers Finally Get to Explore 'Blue Hole' Mystery Cave New Mexico site has been sealed for nearly 40 years By John Johnson, Newser Staff Posted Sep 14, 2013 10:25 AM CDT Updated Sep 14, 2013 10:52 AM CDT 16 comments Comments (Shutterstock) (Newser) – The last divers to venture into an underwater cave known as the "Blue Hole" in New Mexico were from the state police in 1976, and they were there to retrieve the bodies of two young divers who died while exploring. Upon exiting, the police divers sealed the opening with a grate that has kept anyone else from getting inside—until this weekend, reports LiveScience. Expert divers from the ADM Exploration Foundation have gotten permission to remove the grate and see just where the Blue Hole leads. (This kind of cave diving is not for novice divers, explains a post at Gadling.) "We really have no idea what exists beyond the grate," says a city official in Santa Rosa, maybe not coincidentally its tourism director. Perhaps the cave leads to a network of other caves? “We hope to discover large subterranean passages,” the ADM team leader tells the Albuquerque Journal. The police divers thought the Blue Hole was at least 225 feet deep, and the ADM folks will have equipment to get them to 350 feet. It's also possible, of course, that they'll be disappointed. One diver who went down in 1974, before the grate went up, thinks the police equipment overestimated the depth. He pegs it at 130 feet, max. We'll know soon enough, because the ADM team plans to map the cave and take video all the while.