Harry and his dive buddies ventured farther, excited to explore a portion of the wreck that was usually off limits.

He and two others moved in while the fourth in their group decided to hang back by the entrance. Entering a corridor they were certain would lead out of the wreck, they turned a corner and ran into a cloud of silt. Viz dropped to zero, and Harry didn’t know which way to go. But he knew one thing for certain: He was low on air.

THE DIVE

Four divers explored the shipwreck, which rests at 140 feet, both inside and out. The group was on its second day of diving the wreck after two successful and uneventful dives the previous day. Harry, a 51-year-old with technical diving experience, and the others planned to penetrate areas that were considered off limits. A mutual friend, who was not along on the dive trip, told them that barriers to the engine room had recently been removed and that they could see part of the wreck few had explored before. That was all the motivation they needed. The off-limits area contains narrow passageways that make it easy to get lost and are dangerous to navigate in full gear. Over the years, divers removed some of the chains and welds so they could gain access.

THE ACCIDENT

The group progressed through the early portion of the dive without incident. The divers entered a small room within the lower decks of the ship, and one diver decided to wait there. The remaining three continued on. Without realizing what they were doing, the divers stirred up a considerable amount of silt behind them.

The fourth diver waited as long as he could, but got dangerously low on air. He realized he needed to surface on his own. The diver ascended all the way to the dive boat to let the crew know his friends were inside the wreck. Then he dropped back to complete a safety stop at 15 feet using a tank the boat crew staged over the side. The tanks he carried were empty.

Two crew members from the boat quickly donned their gear and descended to the wreck. Within a few minutes they located Harry’s body and brought him to the surface. It took additional divers to locate and bring the remaining two divers to the surface the next day.

Emergency personnel rushed Harry to the hospital, but he was pronounced dead on arrival. After the other bodies were recovered, an investigation of their equipment showed that all their tanks were empty. Autopsies reported the cause of death as drowning. The equipment investigation indicated the divers were carrying lines and reels with them, but for unknown reasons they did not use them when they entered the wreck.

ANALYSIS

Any overhead diving environment carries additional risks. Any time there is something between you and a direct ascent to the surface—whether it’s a cavern, cave, wreck or ice—the situation requires additional training, equipment and preparation. Dives that require mandatory decompression are also considered overhead environments. There isn’t a physical barrier between you and the surface, but ascending without making a decompression stop increases the likelihood of decompression sickness.

Silt accumulates in areas where there is very little current or circulation underwater. Sediment and particulates in the water get trapped inside structures and settle out on the bottom. Over the years, silt can accumulate into piles of fine powder several inches thick. An errant fin kick or hand movement can stir up the sediment, making it impossible to see.

Divers trained in wreck penetration or cavern and cave diving learn fin-kick techniques to move themselves through the water without directing force toward the floor of a wreck (or the bottom of a cave) that would stir up silt. This is an important part of the training necessary to be able to dive in these environments.

There is no way to know why the divers in this case didn’t use the lines and reels they had with them, but their use would likely have increased their survival chances. The accepted practice for a dive like this is to use a guide line that assures you can find your way out of the wreck, even if you otherwise get disoriented or caught in a silt-out. That way, you can reel the line back in and find your way past the area of impaired visibility. Although there can be concerns about lines getting cut or entanglement, proper reel use and line placement are part of the training needed for this kind of diving, and are no reason not to use a guide line.

The wreck rested at 140 feet, meaning the average depth of this dive was likely between 120 and 130 feet of seawater. At those depths, the no-decompression limits would be 10 to 15 minutes, according to the U.S. Navy Dive Tables. To make a penetration dive at those depths, you should bring along additional air supplies and plan the dives as decompression dives to give yourself time to explore the wreck and make it back to the surface safely. To manage the risks, technical penetration dives like this require specialized training and equipment.

Any diver can call any dive for any reason. In this situation, the fourth diver chose not to go deeper inside the shipwreck. For whatever reason, whether he was low on air or just didn’t feel comfortable with the dive and the situation, that decision saved his life. It’s never worth putting yourself in a dangerous situation outside the limits of your training.

Do not make dives you aren’t ready for or aren’t comfortable with. Too many divers go ahead and make dives they aren’t prepared for, and end up being part of this column.

LESSONS FOR LIFE

■ Seek training in overhead environments. Don’t enter areas you aren’t trained or pre- pared for.
■ Use your common sense. And don’t become overconfident in your skills.
■ Call a dive if you don’t feel comfortable with the plan or the situation. You can always come back another day.

We're often asked if the Lessons for Life columns are based on real-life events. The answer is yes, they are. The names and locations have been removed or altered to protect identities, but these stories are meant to teach you how to handle a scuba diving emergency by learning from the mistakes other divers have made. Author Eric Douglas takes creative license on occasion for the story, but the events and, often, the communication between divers before the accident are entirely based on incident reports.

Read More Lessons for Life