Reported StoryTwo divers in their 30s did a quarry dive to a depth of 48 fsw (16 msw). The visibility was 10-15 feet, and the bottom was covered with mud and silt. Diver One used double cylinders configured to Hogarthian standards: dual cylinders mounted on a back plate with a bladder-style buoyancy compensator device (BCD), connected together by a separator manifold and dual valve posts. The octopus and gauges were mounted on the left post; the inflator and primary regulator with a long hose were mounted on the right post. He had made 50 dives since his initial certification.
Diver Two used a single cylinder mounted on his back, a standard BCD and gauges and was equipped with two regulators, octopus and primary regulator as is common in recreational diving. He had made 10 dives since becoming certified.
At one point during the dive, Diver Two exchanged his primary regulator for the octopus regulator. This triggered the primary regulator to start free-flowing air. After several attempts to stop the free-flow, Diver Two placed the primary regulator back into his mouth, where it finally stopped free-flowing. However, due to the free-flowing, his tank was empty. Diver Two signaled to Diver One, asking for his spare regulator. Diver One took his primary regulator on a long hose from his mouth and handed it to Diver Two.
Unfortunately, the long hose did not come free of Diver One's harness, and Diver Two started forcefully pulling the hose for more length.
Meanwhile, Diver One reached for his spare regulator, which had become entangled and was upside down. Diver One tried to breathe from the inverted regulator, which was leaking water through the purge valve and consequently caused him to get a lot of water through his regulator and not enough air. Diver One bolted to the surface with Diver Two being dragged along with him by holding onto Diver One's weight belt. Fortunately, both divers reached the surface without sustaining injuries.
CommentsThe Hogarthian gear configuration — proposed by cave diver, William "Bill" Hogarth Main, allows for an easy arrangement and deployment of dive gear and accounts for required redundancy and prevention of possible failure events. The configuration consists of two cylinders mounted on the back plate with a bladder-style BCD between the plate and cylinders. A separator manifold joins the tanks, allowing the diver to isolate his left and right cylinder in the event one regulator starts free-flowing. This gives the diver a controlled reserve of air as one cylinder is emptied.
Primary and secondary regulators are mounted on separate cylinders on opposite posts, allowing the diver to switch regulators if necessary. One regulator is on a long 7-foot (2-meter) hose; the other is on a standard-length hose. The primary goes under the arm, across the chest and around the neck into the mouth, while the secondary is ready to use, located just below the chin and held in place by a bungee cord loosely wrapped around the diver's neck. This is supposed to make it easier for buddy assistance in an emergency. In the past, this configuration was used solely by technical cave divers, but it has recently been adopted by some recreational divers.
The basic philosophy behind the Hogarthian configuration for technical cave diving can be summarized as "Keep It Simple, Stupid!" (KISS), which means take only what you need on a dive. However, the Hogarthian configuration may become an issue for recreational divers and their buddies when gear styles are mixed. This case was such an example.
Regulator free-flow was the first adverse event in this incident, occurring when Diver Two tried to switch his regulators. Some regulators are so sensitive that they will free-flow when out of a diver's mouth. Free-flow can also occur when debris get into the regulator — for example, when a regulator gets dragged over the silty floor. Diver Two was not prepared for this situation; while he was trying to stop the free-flow, his tank emptied.
Diver One, who had a Hogarthian configuration of his dive gear, was prepared in theory to provide help in an out-of-air situation. He handed his primary regulator, which he knew was working fine, to his distressed buddy. Ideally, Diver One would tilt his head forward to allow the loop of the hose to come off easily and allow his buddy to stay at a comfortable distance and breathe from his tank. This did not go as smoothly as expected in this scenario when the two divers attempted buddy breathing, creating the second adverse event. While Diver Two was pulling on the hose of the provided regulator, Diver One had a difficult time reaching his secondary regulator, which became entangled and caused Diver One to not get enough air, the third adverse event.
Diver One bolted to the surface — the fourth adverse event — while Diver Two hung onto him —the fifth adverse event. Fortunately, the surface was not far away and the divers were not injured. There is no gear configuration that will allow for a safe dive if the diver is not prepared. In this case, Diver Two was not prepared to handle regulator free-flow, which occurs frequently, thus every diver should be able to resolve it. Some regulators have a dive-predive switch that makes them less sensitive when not used. Most free-flow will stop when the mouthpiece is turned downward or if a few fingers are placed across it. In the case of persistent free-flow due to debris or frosting, the diver should be able to get enough air to make a controlled ascent to the surface. Neither Diver One nor Diver Two were prepared to hand out and use the regulator on a long hose in an emergency situation.
When divers are diving with others who have different diving configurations, it is very important that both divers know each other's equipment. Extra time should be given prior to the dive for one buddy to explain to the other what gear configuration they are using and how it is deployed. It is also a good idea to do a dry run of an out of air emergency prior to the dive. Each buddy should know how to locate and deploy the required equipment simulating an actual emergency. This practice could have reduced the stress and likelihood of the adverse events that led to this incident.
— Brian H. Wake, PADI Course Director and TecRec Instructor Trainer