Ed.'s note: This regular column presents the anatomy of a diving accident and the lessons to be learned from it. The incidents described are real. Names of locations and people have been changed or deleted.

It is often said that Murphy is alive and well — or at least his law is. When things go wrong, your predive plan can be critical to survival. Take the case of a hapless group of advanced wreck divers.

The Dive

Off the coast of Southeast Florida in the strong currents of the Florida Straits, our group of divers set off for an advanced wreck dive. The group consisted of Shawn, a wreck instructor, and two students, Tom and Ben. The students had signed on for a wreck-penetration course combined with an advanced decompression procedure course. They were in their third day of diving, and the goal was a no-penetration dive to 165 feet on the wreck of the Hydro Atlantic. The dive plan called for the divers to complete drifting decompression because the strong currents made hanging on an anchor line uncomfortable at best.

The divers intended to drift below bright-orange lift bags using buddy lines, if necessary, to keep the group together. Dive preparation, setup, briefing and water entry took place without a hitch. Then, Murphy reared his ugly head. Ben experienced an unresolvable violent second-stage free flow at 140 feet approximately five minutes into the dive, forcing the divers to execute emergency protocols. Ben shut down his malfunctioning equipment, switched to his alternate and signaled the dive group to abort the dive. The divers removed and deployed their bright-orange surface marker bags and ascended to 15 feet for a five-minute safety stop.

The Incident

Unfortunately, Murphy was very industrious this day, and the boat crew failed to see the surface markers when they broke the water's surface nearly 25 minutes ahead of schedule. Currents were very swift, and by the time our divers slowly ascended, completed a safety stop and surfaced, the boat was a mere speck on the southern horizon. They drifted freely in the Atlantic Ocean for an hour before the captain became alarmed. As our divers drifted into deeper water, the current accelerated and their passage northward also accelerated. The group drifted in the ocean for nearly three hours beyond the planned dive time before rescue was effected.

The Rescue

Fortunately, our dive group was well-prepared. They each carried sonic signaling devices, aerial flares and two large surface marker devices, one of which was colored in international orange. The instructor gathered the students and used buddy lines to keep the group together. They inflated all of their markers to create a larger target to see. After trying unsuccessfully to signal two passing boats, the instructor sent up an aerial flare, which went unanswered. The group then drifted for approximately an hour without another vessel in sight. Upon seeing another vessel on the horizon, the instructor sent up his second aerial flare. The vessel acknowledged the flare and immediately approached the divers, picked them up and returned them safely to port. Other than minor hypothermia, the divers were none the worse for wear and returned to port with a much greater appreciation for their emergency signaling equipment.

What Went Wrong

Although the instructor had booked his charter with a reputable dive facility, the facility's regular captain was unable to work that day, and a part-time replacement was called in. The replacement captain was accustomed to working with drift divers, but had no experience with groups doing advanced, deep wreck work and had never done that type of diving himself. Although the captain participated in the detail briefing, he failed to understand what would happen if the divers had to abort the dive early. Apparently, when the surface markers broke the surface, he was below deck and was not observing the area. He later recalled seeing the markers at a distance but assumed that they were in use by some of the drift divers who frequent the area. Therefore, he made no attempt to maintain visual contact or to pick up the attached divers.

What Went Right

The success of this rescue began long before the dive. Our divers were well-equipped with two surface marker buoys, two aerial flares, tank-powered sonic alert devices, strobe lights and two chemical light sticks even though the dive was planned for midmorning on a bright, sunny day. When it became apparent that pickup was not imminent, the divers used buddy lines, frequently used by advanced divers for safety stops or deco stops, to keep the group together and to deploy additional surface markers to make the most visible target possible. The instructor then had the divers switch to snorkels in order to conserve tank air for the sonic devices while avoiding the intake of salt water. Additionally, the instructor gave each of the divers minor tasks to perform to help ensure that they remained calm while awaiting rescue.

Lessons For Life

When diving in open ocean:

• It is important for all members of the dive team — including, or perhaps especially, the boat captain — to understand all facets of the dive plan.

• Carry proper signaling equipment. While the equipment used by these divers maybe excessive for the average recreational diver, sonic and visual signaling devices should be carried by every diver on every dive.

• Always plan for contingencies.

• Conserve expendable signaling equipment until it is useful. Flares are pointless if there is no one to see them, and battery-powered lights are ineffective in bright daylight.

• If you're with other divers, take whatever action is necessary to stay together.The larger the target, the easier it is to spot.

• When drifting, continue to breathe tank air or switch to a snorkel to avoid inhaling or swallowing salt water.

• No matter how bleak the situation, maintain a calm demeanor and a level head. Taking actions to improve your situation helps stave off panic.