It was probably a screw-up or misunderstanding on the part of the reporter. Maybe they were 260 ft from the entrance. Hard to believe they dived to 260 ft deep - if they did, what the hell were they thinking? Nitrogen narcosis would be very likely if diving to that depth with normal compressed air, from what I understand.
A whole list of things can go wrong at that depth, oxygen poisoning and nitrogen narcosis being only two. And with normal air in a compressed tank at that depth? You’re basically dead.
Looking at the picture of the spring they dove, it does not look 260 feet wide. Hence, they probably were found at 260 feet down. That does not mean they died at 260 feet down. They may have sunk that far after dying.
When I read they went down 260 ft, I thought, "Dang, they were on mixed gas for a cave dive!" But, I think you're right, the reporter mixed up distance with depth.
It may have actually been that deep.
When I was a kid in the early 60s or maybe late 50s a diver drowned in Morrison Springs at something close to 300 feet. I guess my memory could be off a bit.
Lloyd Bridges came but when he found out how deep he was, he said it was too deep.
It took a while but finally some kids from Auburn got the body out.