Eli Marchetti had been cave diving for nineteen years when he became trapped behind a silt-out at roughly 1,400 meters of penetration in a north Florida cave system on the afternoon of June 3, 2025. He was on a solo exploration dive, a practice his certifying agency does not endorse but which is common among experienced cave divers in the region. He had filed a dive plan with a support team on the surface and was carrying redundant gas, redundant lights, and a reel of new line he was attaching to existing main line in a side passage.

The silt-out happened in a section of low ceiling where his fins, despite his care, had stirred a layer of fine sediment that had settled on the floor. Within seconds, his visibility went from perhaps six meters to absolute zero. He could see the glow of his light against his mask, but nothing else.

He was 1,400 meters from the entrance, at a depth of 36 meters, with approximately 180 bar in each of his back-mounted tanks and a full stage bottle of bailout gas slung beneath him.

He took twelve hours to reach open water.

Marchetti, 47, a structural engineer from Gainesville, has written about the experience in a long technical post on a cave diving forum, which he later expanded into a presentation at a regional cave diving workshop. The account is unusual for its level of operational detail and for its near-total absence of drama.

When the visibility in the Florida cave dropped to nothing, Eli Marchetti had two choices. He chose the slow one. It took him twelve hours to reach open water.

The protocol for a silt-out, in cave diving, is straightforward to describe and difficult to execute. The diver makes contact with the guideline, confirms direction toward the exit, and follows the line out by touch. The line is the only navigation. The diver cannot see, cannot rush, and cannot make assumptions. If the line is broken or lost, the diver runs a search pattern from a fixed reference. If the search fails, the diver dies.

Marchetti made contact with the line within four seconds of recognizing the silt-out. This is the figure he has emphasized most in his retellings. He had practiced the touch contact drill many hundreds of times in open water and in shallow caves. He attributes his survival, in large part, to the fact that the drill was reflexive.

He confirmed direction by feeling for the line markers, small plastic arrows that point toward the nearest exit. He found one within a meter of his hand. He began the slow exit, hand over hand, with the line gripped between thumb and forefinger and the rest of the hand kept loose, in the position cave divers call the okay grip.

The cave was not straight. There were restrictions, T-intersections, and one section where the line crossed itself in a way that, in zero visibility, required him to stop and feel both directions to determine which was the exit. He carried a small slate on which he made notes by touch. He used the slate three times in the twelve hours.

The gas planning was the other variable. Cave divers plan gas using a rule called thirds: one third for the way in, one third for the way out, one third in reserve. Marchetti had executed the rule conservatively. Even so, twelve hours was more than four times the duration of his planned dive. He extended his gas by reducing his work rate to the absolute minimum, by switching to his bailout bottle when his back gas reached the planned reserve, and by holding decompression stops at depths that maximized off-gassing while minimizing breathing resistance.

He surfaced at 4:11 the following morning. His support team had been on the verge of activating a recovery, which in cave diving is generally a body recovery. The team's coordinator, a longtime friend named Joanna Reyes, has said publicly that she had begun the phone calls she had hoped never to make. She made one of them, to Marchetti's wife. She had to make a second call, twenty minutes later, with very different news.

Marchetti was treated for mild decompression sickness and for exhaustion. He was hyperbaric-treated at a chamber in Gainesville. He was back at his desk within a week.

He has not stopped cave diving. He has, however, stopped diving solo. The decision, he has said, was not driven by the silt-out itself, which a team would not have prevented. It was driven by what he thought about during the twelve hours on the line, which was, mostly, his wife and his two children. The presence of a teammate would not have changed the physics of his exit, but it would have changed who was there if he had not made it.

He is active in the regional cave diving community as an instructor for the touch contact drill. He teaches it in open water first, with blacked-out masks, and then in shallow training caves. He says, in his classes, that the drill is the cheapest insurance policy a cave diver can buy, and the one most often allowed to lapse.

He keeps the reel he was running that day. The line is still on it. He has not used it again.