Case Summaries

Omitted Predive Buoyancy Check Leads to Trouble

Scuba diver survives a life-threatening hazard caused by the omission of the predive buoyancy check.

Reported Story

The diver is a 51-year old male, measuring 71 inches (180.5 cm) tall and weighing 270 pounds (122.5 kg). His dive experience consisted of 72 lifetime dives up to a maximum depth of 120 fsw. He considered his skill level as intermediate. He reported an incident that occurred on a wreck dive while using a drysuit and compressed air.

Here is his report.

I failed to do a buoyancy check before the dive, and immediately it became obvious that I was overweighted as I entered the water. I tried to swim directly down to the wreck instead of going to the front of the boat and descending along the line that was fixed to it. I got swept in the current and dropped to the bottom away from the wreck. The other divers could not find me. I eventually made a safe ascent, did my safety stop, and all was OK.

A look at the log below shows that I started sinking rapidly.


I was at 77 feet one minute into the dive. I added air but began ascending too quickly. My computer issued a rapid-ascent warning at about 60 feet. I started venting but continued ascending until about 45 feet, then I started sinking again. I reached 98 feet in four minutes.

At this point, I was able to see the bottom and look around. I swam over to the wreck and grabbed on so that I wouldn't be swept away by the current while gathering my thoughts. At five minutes into the dive I was at the bottom at a depth of 102 feet. I hung out there for about five minutes, assessing the situation; then I started swimming toward the shoal, which gradually rises to 60 feet. I noticed the line going up and reached it at about 12 minutes; I followed it up to about 43 feet below the surface. I stayed there for a few minutes to off-gas somewhat.

Trying to get my buoyancy right, I was up and down the line a bit until I decided to go for the surface at about 17 minutes. I started ascending too quickly, vented and dropped down to 60 feet. The rest of the dive is up and down, trying to stay down long enough to get my three minutes at 10 feet.

This is how another diver saw my incident:

D entered the water overweighted. The tank he rented had a different buoyancy than the one he was used to, and he wore a drysuit that he was not familiar with. Upon entering the water, D failed to do a weight check. When D vented his suit, the overweighting took over, and he descended uncontrolled straight to the bottom. D attempted to ascend, but because of the overweighting he had to apply a large amount of air. The large volume of air expanded quickly and caused a runaway ascent. To resolve this, D vented air, but he vented too much and sank again. This process happened repeatedly until D was able to control the venting and adding of air better and safely make it back to the surface.

Comments

Buoyancy problems
Buoyancy problems are often the root cause of diving incidents. In this case, the diver was at risk of barotrauma due to the rapid ascent, running out of air due to frequent adjustments of the buoyancy vest, overexertion, drowning and decompression sickness. Fortunately, the situation resolved without injury. The need to practice buoyancy-control skills regularly and conduct a predive buoyancy test whenever a new configuration of equipment is used cannot be overstated.

Fitness to dive
This was an obese diver using medication for several medical conditions along with vitamins and supplements. Based on the information provided in the report, it appears that there are several issues that may affect fitness to dive in this case:

  1. Obesity (BMI 37.7)
  2. Indications of cardiovascular disease; risk of cardiovascular disease
  3. Combination of drugs that may be dangerous

However, it is up to the diver's physician, who has full insight into his health and physical fitness status, to decide the diver's fitness to dive.

We asked for more details about the diver's medical history, which were readily provided, but it is not appropriate to discuss them in detail on a public forum like this when identification of the diver is possible. Here are some of the questions and answers that may add some but not complete insight:

  • Did you have an evaluation for possible heart disease?
  • Maybe. I recently had what is called a heart scan. Using ultrasound, they listen for blockages in your neck, arms and legs to make sure that the blood is getting everywhere and not blocked. I had no issues.

  • Do you exercise? What kind of exercise, how often, and how long?
  • No, not really. Every once in a while I will exercise for a week or so, but I never stay with it.

  • How many dives using a drysuit did you have before this incident?
  • About a dozen or so, and I did take and pass a drysuit course. I have never really felt comfortable in mine though. It has always leaked, and I continually have problems with it. The dive shop where I bought it is very good about helping me with it, but there is a huge frustration factor.

We learned that this diver is doing pretty well when it comes to medical control, but he could do more when it comes to managing his lifestyle. He has been under thorough medical supervision. His personal physician prescribes all his medications, and it's important to control the risk of possible bad interactions between the drugs. He consistently has an annual medical checkup.

Recently, he did a more extensive evaluation of his cardiovascular risk factors by undergoing a heart scan, which was within the normal range. He does not smoke and does not drink excessively (up to two drinks per week), but he does not exercise enough. His energy balance is on the side of weight gain because his food intake exceeds his energy consumption through physical activities. This is an area in which he should consider improvement to increase his safety margin in diving. (See "Improving Cardiovascular Endurance").

— Dr. Petar J. Denoble