Alert Diver Article
To Dive or Not to Dive
April 2002 Issue
By: Gil Zeimer & DAN Staff

DAN Asks: When Do You Decide It's Time to Cancel A Dive or Even Pass It Up?

A tough decision certified divers sometimes have to make is when to cancel a dive or forgo a second dive after something has gone awry. Many divers in the Incident Insight cases profiled bimonthly may have avoided trouble had they aborted their dives and given themselves 12 or 24 hours to start again. Aside from the frustration of paying for your dive and then not making one, divers often don't want to appear weak or hesitant. Also, they may have invested a lot of time in the planning and travel for this dive.

The DAN member describes a simple problem that led him to abort a dive and to try again under more favorable conditions. He made a wise and positive choice. Often unexpected weather conditions, sudden illness or equipment difficulties intervene when we're diving. Or we make a mistake on the first dive and can't really make up for it without skipping our second dive. All are good reasons. Like our diver, better safe now and dive later, than sorry all around.

Following the Member's story of his aborted dive, the DAN Medical Department offers some examples of cases we've addressed over the years. They may help divers identify when not to continue diving.

The Story:

I hadn't been underwater in a few years, so I'm always more cautious on my first dive of the trip. This day, the wind off the Florida coast in late February was gusting to 20 mph / 12.5 kph and the seas were rolling with 3- to 4-foot / 1- meter-high waves. I jumped in to follow a divemaster and six divers to a depth of 85 feet (25.5 meters) on a drift dive.

My mask fogged up entirely when I hit the surface. I tried to clear it, but I couldn't. I submerged a few feet and took it off, wiped it, and put it back on. It was still almost completely fogged.

With the surging surf, the visibility was about 30 feet (9 meters); I could see only the bubbles of my companions. As I descended, trying to follow the bubbles, I thought to myself, "This is a potentially dangerous situation. I'm alone. The divemaster doesn't know I'm up here; he can't see me and I can't see him. My dive buddy can't see me either. And if I surface too late, the boat won't be able to spot me because of the strong current and the waves."

I also thought of my wife and daughter who were with me on the vacation: they were the most important reason not to let anything happen to me.

After 10 minutes of trying to find my group, I aborted the dive. The boat motored right over to me. I climbed on. And that was it. I was safe, not sorry. About 90 minutes later, I took my second dive with the group, and it was wonderful.

- DAN Member Gil Zeimer

The Commentary — The Dangers of Rapid Ascents

Over the years we have talked to many divers who could have saved themselves lots of trouble by just making one less dive. It's hard not to go on and make dives that are already paid for. Most injured divers only realize their mistake after they begin having symptoms or when they have trouble while in the water.

DAN gets calls from divers on the 24-Hour Diving Emergency Hotline and the Dive Safety and Medical Information Line after something goes wrong on dives, and when divers are afraid they will get decompression illness. Certainly DCI is always possible, but getting DCI depends on the divers' dive profiles and actions during their dives.

The most common call to DAN is about a rapid ascent. The call starts out: "I made three dives today, but on the first or second dive, I had an uncontrolled ascent, my computer was beeping at me, and I didn't do my safety stop." The diver is sure he'll start feeling symptoms soon. Some may, but most will not.

Rapid ascents violate the theories behind dive tables and dive computers. This is similar behavior to spending more time than allowed at any given depth during a dive. If you accept that safety stops are now part of the standard diving procedures, then missing a safety stop could also be considered a violation of one's own dive plan.

Both of these violations - rapid ascents and missed safety stops - show up in the DAN dive injury database. Safety stops can't guarantee DCI-free diving, but, by slowing the ascent near the surface, they can probably reduce the incidence of cerebral gas embolism, a serious and more immediate type of DCI.

Avoiding a planned safety stop after long, deep or repetitive diving can present a problem: according to the DAN dive injury database, rapid ascent occurs in 25 to 30 percent of all injury cases. Even if divers make safety stops, they still have some risk of DCI.

A rapid ascent or a missed safety stop should pose enough of a concern for a diver to abort a current diver and / or call off the next planned dive.

Most symptoms begin within two hours after a dive, after which the risk of symptoms increases. The trouble is that the surface interval between most boat dives is not two hours: making additional dives can compound any mistakes a diver may make on the first or second dive. If a diver makes a mistake on an early dive and the nitrogen exposure is high from deep or prolonged dives, a rapid ascent can become an even greater risk.

On shorter, shallower dives with minimal exposure, divers do not have the same risk of DCI. So, what to do? If you're in the greater risk group with table or computer violations, it is safer to sit out the next dive; dive again after a long surface interval. The longer a diver spends out of the water, the more nitrogen he'll offgas, and the lower his risk of DCI with repetitive diving.

Each individual is unique, so there will be variations among different groups of divers. For example, someone in a group of divers gets DCI after making the same dives as everyone else in the group. Rarely do we see more than one person with DCI in the same group of divers. Why that person and not the others? Part of the explanation may just be some of these minor violations that divers commit. Each diver must accept the risks implicit in diving, and deciding not to dive sometimes should be an option for safer diving.

- Joel Dovenbarger, BSN, Vice President, DAN Medical Services

The Perils of Motion Sickness

For the person suffering motion sickness, there are many compelling reasons to "cry mutiny" and abandon that offending vessel. However, it's probably better to stop and think for a moment before diving into the water. The effects known to produce motion sickness - spatial disorientation, angular accelerated motions, as well as emotional factors - are all easily and quickly identified underwater. And even though jumping ship to make that dive may seem like a reasonable solution to motion sickness, the disabling symptoms may, at the very least, turn that dream dive into a nightmare.

Many have experienced the characteristic sweats and pallor, yawning and salivation, followed by nausea and vomiting. These normally result from physiologic vertigo, which includes motion sickness, space sickness and the vertigo experienced by some people when exposed to heights. The inner ear detects motion, yet the eyes do not detect anything in motion. The effects of poor visibility and restrictions imposed by the mask often distort one's vision, and the weightless environment may alter the clues normally provided by gravity. Moreover, the consequences of dehydration, caused by vomiting and the lack of normal fluid intake, are oftentimes considered an important contributing risk factor for decompression illness. Add the effects of anxiety to this mix, and a panic situation can follow.

Before diving, the seasick diver may do well to consider the risk versus the benefits of taking the plunge while feeling ill. Take a moment to reflect on the possible consequences of vomiting underwater (e.g., water aspiration and / or equipment malfunction); the effects of weakness and inability to concentrate; and the risk the condition presents for other divers who may have to provide aid. Remember, good judgment is an integral part of safe diving.

- Daniel Nord, EMT-P, CHT, Director, DAN Medical Services

Canceling a Dive: Cave-Style

If buoyancy skills and diving skills are not perfect, a diver shouldn't venture into an overhead environment - a cave, cavern, shipwreck, lava tube or any similar structure. One's survival demands such skill. Each year DAN fatality statistics list so-called "rec-tec" divers who have no formal training in cave or cavern diving, but they attempt to perform a dive beyond their skill and end up among the fatality statistics.

One of the basic rules of cave diving is: "Anyone can call the dive for any reason at any time without anyone questioning it or fear of repercussions."

A diver who is not at his 100 percent best may endanger more lives than his own. There is no room for error when a diver is a half-mile (1,000 km) into a tunnel, with no access to the surface. Furthermore, such a diver may also have a decompression obligation that precludes safe direct ascent to the surface after leaving the tunnel.

Safety is no accident; one should be both thorough and smart about it. Cave diving is no place for cutting corners. All the same safety precautions and attitudes apply to open-water divers (with direct access to the surface). The difference lies in the caver's approach. Every dive has the potential for enormous enjoyment and risk. Safety can be found in the balance.

-- Celia Evesque, NREMT-I, DMT, DAN Medical Information Specialist

Reasons to abort a dive in progress (add your own):

1) Conditions not optimal for planned dive;

2) Equipment malfunction that necessitates using backup equipment (leaving no other backup): i.e., lights or regulator failure;

3) Excessive silting, whether in open water or in an overhead environment;

4) Not "feeling right," particularly seasickness;

5) Weather conditions are deteriorating.

Possible reasons to cancel a future dive:

1) Equipment malfunctions (regulator free-flow, drysuit problems, etc.);

2) Exceeded planned parameters of previous dive that day that may have led to excessive tissue loading (i.e., went into deco without really planning for it);

3) Weather conditions (i.e., wave action, current too strong, etc.);

Possible reasons to exceed table / computer algorithm parameters with obligatory decompression to follow:

1) You have adequate gas to complete or exceed dive parameters plus mandatory decompression requirements (you must know exactly what you have available).

2) Team member is in trouble; it may take longer to complete dive safely.

3) Life-or-death situation that necessitates violation of decompression tables/computer algorithm; a recompression chamber visit is preferable to drowning.

© DAN -- Alert Diver April 2002