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Scuba Professional: Column No. 6




School’s Out!

When is a technical dive not a technical dive? When complacency sets in, even the most experienced of scuba divers can make mistakes that could cost them their lives…

The group of four guys who star in this story are all instructors and trained technical divers. One day last year they decided to go out on a dive to look for manta rays and mola-mola, the oceanic sunfish that Bali’s Nusa Penida is famous for attracting at certain times of the year.

It would just be the four of them: no new divers or guests around to distract them or spoil the fun. They were aware that the search for the mola-mola could take them into deep water, so they were all equipped with back-mounted double cylinders or twin side-mounted independent single cylinders. A couple of them had just completed a sidemount course in open water and were practicing with this new configuration. Their back gas was air and they also had decompression cylinders on the boat filled with NITROX 40.

As they were gearing up on the boat, one of the divers clipped on a decompression cylinder but the other three decided against carrying an extra cylinder on the basis that it would just over-burden them.


Crystal Bay, Nusa Penida

What a Dive!

It was an eventful dive. They descended on to a shallow cleaning station and immediately found a group of manta rays sweeping in to get serviced. However, the ocean swell crashing against nearby cliffs and then rebounding made it difficult for the divers to maintain their position in the water. They often had to swim hard against the surge to keep the mantas in view.

Once they had seen enough manta action they headed into deeper water away from the cliffs in search of a thermocline and, they hoped, some mola-mola hiding in the cooler water below. At around 36m they found exactly what they were looking for.  A blurry shimmer in the sea announced the presence of a cool upwelling. Two enormous sunfish were lurking beyond, the parasites on their large disc-shaped bodies being picked off by a school of black, yellow and white bannerfish.

The divers were understandably excited and stayed watching and photographing the sunfish for several minutes. Looking at their computers they knew they had gone into decompression but they were quite relaxed about this. After all, they all had at least two cylinders. They could think about taking care of whatever decompression burden they had accrued when they eventually got back to the shallows. Unfortunately, none of the divers were monitoring their air supply closely so they didn’t realise that the combination of the surge, the depth, the cold water and the thrill of seeing all the big fish had caused their breathing rate to increase.


Mola-mola and diver, Nusa Penida

The Fun Turns Serious.

It was the diver with the decompression cylinder who noticed first. He glanced at the gauges on his side-mounted twins and saw to his surprise that he had only 40bar and 60bar remaining. He signalled to the others that he was ascending and started to move up beyond the thermocline and back towards the shallows. After a few minutes he felt a tug on his arm and turned to find one of his buddies showing him that the pressure gauge on his doubles was reading 20bar. After a few minutes of confusion, during which they used up even more of their rapidly diminishing breathing supply, the diver who had the most air unclipped his decompression cylinder and passed it to the other diver. They then both headed up to start their decompression stops which by then totalled over 30 minutes.

Focussed completely on their own problems and buffeted by water movement in the shallows, the two divers drifted apart and became separated. The diver who now had the decompression cylinder was fine. He completed his stops comfortably and eventually ascended alone and returned to the boat.

The other diver was now regretting handing over his emergency gas as it dawned on him that, without it, he no longer had enough gas to complete his own decompression. The sight of the other two divers coming towards him raised his hopes. However, they were swiftly dashed when he saw what their gauges were showing. They were in exactly the same predicament as he was.

With air supplies down to almost zero, the three divers decided that their best option was for one of them to go to the surface, omitting his remaining decompression stops, swim to the boat, get a couple of full cylinders with regulators attached and come back down with them. The diver with the least amount of decompression time remaining bravely volunteered.

Luckily, all the divers survived unharmed. The diver who had blown his stops and redescended spent the journey back to the dock breathing emergency oxygen as a precaution but he felt no symptoms of decompression illness. Nobody spoke much on the return journey; it had been a chastening experience.

While the Cat’s Away

There is a popular maxim that says, “While the cat’s away, the mice will play.” There they were, all good divers who knew what they were doing, on a fun dive looking for big fish. There was nobody else around: no technical instructor to judge or reprimand them: no trainee divers who might follow their example. School was well and truly out! So why not just relax and let the rules slide for once? No need to worry about planning. They all had two cylinders and lots of air. If they ran into a bit of deco, they would just do the stops. What could go wrong?

Telling the story later, they described this as a technical dive. This was not a technical dive. A technical dive has pre-set parameters and is planned in detail with potential risks assessed and prepared for. This was just a deep, long dive in difficult conditions approached casually and carelessly by a group of divers who should have known better and who could have ended up paying for their carelessness with their lives.

The certification cards they hold show that they were all trained in decompression diving procedures by good technical diving instructors and all had the skills to execute a deep, long dive successfully. They had all planned a number of complex technical dives in the past and knew how to calculate gas requirements, compute decompression plans and work as a team to ensure the safe return to the surface of all the divers in that team.


Technical Diving. Photo: Andrey Bizyukin

Instructional Issues

So what went wrong?

What they had apparently not been taught sufficiently well is that the rules and procedures for decompression diving apply to all decompression dives, not just dives when someone is looking over your shoulder or when you have students with you. It is possible also that they were not accustomed to taking responsibility for the planning when no technical instructor was around. Perhaps their instructors had taken too much of a hands-on role during their training and had not prepared them adequately for dives when no instructor was present?

When instructors are teaching a course at any level, they must make sure that the students realise that they are not being taught the skills and procedures just in order to pass the course. If you are a student, you must understand that your instructors are not asking you to dive in a certain way just to please them or to satisfy training agency requirements. What you are learning are new habits that need to be practiced beyond the training course, on every dive, whether your instructor is there or not.

Shared Blame

Instructors get used to students depending on them. Many actually grow to like the feeling! However, while dependency may give a boost to the instructor’s ego, it is not at all good for the student. By the final dive in any course, an instructor should be in the role of passive observer. Of course they are still responsible for the successful completion of the dive but they should not be a necessary component for the dive’s success.

The students, as a team, should be able to demonstrate all the skills and knowledge required to complete a dive at the level being taught without the instructor’s intervention or assistance. The reason for this is obvious. On the next dive they do at this level, the instructor will not be there. So if the divers are dependent in any way on the instructor’s presence in order to complete a successful dive, the instructor must add more training dives because they are evidently not yet ready to go out on their own.

Complacency Kills

The divers were exhibiting a mind set common in experienced and professional divers. They may preach the right way to others but at some point they have come to believe that the rules no longer apply to them. This is complacency and complacency kills. There are no occasions when the rules for safe diving can be ignored or bypassed.

Read more from Simon in “Scuba Professional – Insights into Sport Diver Training & Operations” and his bestselling book “Scuba Confidential – An Insider’s Guide to Becoming a Better Diver”, both available from Amazon or iTunes in paperback, e-book and audiobook versions. And if you have friends who are planning to learn to scuba dive, do them a favour and direct them to Simon’s latest book “Scuba Fundamental – Start Diving the Right Way“.

Simon Pridmore is the author of scuba diving books, travel books and, as you might expect, scuba diving travel books. Originally from the UK, Simon has lived in Asia for over 30 years. As well as his books and guides, Simon writes regular columns for a number of magazines. He and his wife Sofie currently live in Bali, Indonesia but spend a lot of time exploring other places trying (but failing so far) to find a cure for their itchy feet. Simon's latest book - Scuba Exceptional – Become the Best Diver You Can Be - the follow-up to his best-selling Scuba Confidential, is available now in paperback and e-book versions from Amazon stores worldwide. Find out more about Simon and his books on

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