The Hernando County Sheriff's Office said two divers drowned at Buford Springs on Wednesday afternoon.
One victim was identified as Todd Richard McKenna, 52, and the second was a 63-year-old man.
The sheriff's office said deputies were called to the springs, which lies in the Chassahowitzka Wildlife Park, around 12:20 p.m.
The 911 caller was a teenager who was there with two others, ages 15, 15, and 17, who were spending the day swimming at the park.
The teenagers told deputies around 11 a.m. the two victims showed up and prepared to dive into the caves while they chatted with the teenagers. The men dove for a short time then resurfaced.
Authorities said the teenagers heard the two men talking about going back down into the cave and believed they heard them discussing if they had enough air in their tanks. One of the men is believed to have mentioned that he may have had a leak in his tank, the sheriff's office said.
The men drove back down into the water and a short time later, the teenagers said one of the men resurfaced face-down. The teenagers said they thought he was looking for the other diver until they noticed there were no air bubbles coming to the surface as they had seen earlier.
The teenagers swam over to check on the man, who was unresponsive. The teenagers were able to get the diver over to a dock but were unable to lift him out of the water, authorities said.
Deputies arrived and jumped into the water. The sheriff's office said they lifted the man onto the dock and he was obviously deceased.
Deputies waited for the other diver to surface but when he didn't they assumed he must have experienced some type of problem in the cave.
Several specialized divers with the International Underwater Cave Rescue and Recovery (IUCRR) responded and searched for the second diver. The sheriff's office said he was found 137 feet below the surface and was also obviously deceased.
The second diver was recovered and brought to the surface.
Neither of the victims showed obvious signs of trauma and both appeared to have the proper diving equipment, the sheriff's office said. Authorities said it's unknown if that equipment was working properly at this time.
The Medical Examiner will determine the exact cause of death.