You don’t have to appear to others as a constant pessimist, you can keep your thoughts to yourself – but always be prepared for that worst-case scenario, advises SIMON PRIDMORE

Always be aware of your trim.

IN THE FIRST PART of this short series, I made a correlation between scuba-diving and driving a car, particularly in the context of learning how to anticipate and assess dangerous situations, make well-informed sensible decisions and stay safe. These are things that motorists tend to group together under the catch-all phrase of defensive driving.

Here are a few more strategies that I see as intrinsic to the defensive scuba-diving concept, where “defensive” carries the same meaning as in the motoring world, that is: safe, careful, conservative and thoughtful.

Appeared in DIVER February 2019


Never follow a divemaster or dive-guide blindly and without question. Never give anyone complete authority over your dive. Scuba-diving professionals are just people. People get things wrong, people overestimate their abilities, people get distracted, people get tired.

Make sure that you are actively involved in all decisions concerning the dive, that you know the dive-plan, understand your role in the team and have an idea of who your fellow-divers are and how experienced they are.

Be prepared to take full responsibility for yourself during the dive, and also be prepared to assist one of your team-mates, or even your divemaster or guide, if they get into difficulty. It happens.


This strategy is similar to the “what if” concept, but whereas “what if” refers primarily to an approach to choosing and configuring equipment, “assume the worst” is more a question of attitude.

There is a parallel here with the advice commonly given to inexperienced drivers always to assume that every other driver on the road is an idiot, and be prepared to act accordingly.

From a scuba-diving point of view, this equates, among other things, to the following:

  1. a) Assume that the person with whom you’re diving is going to get into trouble and is going to need your help.
  2. b) At the same time, assume that you will have a problem during the dive and will have to deal with it on your own.
  3. c) Assume that diving conditions will deteriorate during the dive, and that you might have to abort.
  4. d) Assume that the boat will not be there when you ascend, and that you will have to help the crew to find you.
  5. e) Assume that the boat will not turn up and that you will need a plan B; for example, swim to shore or prepare to be floating for a long time until searchers or fortuitous fishermen come by.
  6. f) Make sure that each piece of your equipment is functioning properly before every dive, but still assume that it is going to fail, just when you need it the most. Be constantly attentive.

There are four main aspects to this:

  1. Replace or repair anything that malfunctions during a dive before the next dive; this includes leaky O-rings and hoses.
  2. Look ahead and think ahead. Early recognition of potential problems gives you more time to react. Don’t forget to look behind you too, especially if you’re in a shipwreck or cavern. You will probably need to pass this way again on exit. Be alert for signs of changing water conditions. Look up to the surface from time to time to see what’s happening there.
  3. Always be aware of how you’re diving and how you look in the water. Think about your trim, how you are streamlined, what your fins are doing and what your arms are doing.
  4. Dive the same way you drive. Watch the ocean as you watch the road. Keep your eye on other divers in the water, as you do other drivers. Anticipate what they might do, and be prepared. A diver with poor fin-control in a confined space can quickly reduce the visibility in that space. A heavy breather can run out of air quickly.

Someone else’s problem can always become your problem too. In my career, two out-of-air divers have torn the regulator out of my mouth (and ripped my mask off in the process) in their desperation to find a source of air to breathe. Neither was part of my group.


Buffers or safety margins are small protective mechanisms that you can include in your dive-plan to make a dive safer.

The strategy of not going deeper than you need to be is a buffer. Making a longer safety stop at 3-6m is a buffer, as is ascending more slowly than the maximum recommended rate of 9m per minute.

Diving on nitrox with your dive-computer set to air is also a buffer. As long as you don’t descend deeper than the maximum operating depth of the nitrox mix, there is no reason why this should not be completely safe.

It is an excellent way to reduce the risk of decompression illness, particularly if you’re on a multi-day dive trip with several dives a day.

Nitrox makes an excellent safety buffer when you use it with your computer set for air.

Always be alert for opportunities like these to add conservatism to your dive.

Classic buffers that have been part of scuba diving since the beginning include going out on a dive, along a reef wall for instance, at a certain depth and then returning at a shallower depth, so you are more likely to be off-gassing on your journey back, as well as using less air at a time in the dive when your cylinder contains less.

Make it a habit to have longer surface intervals between dives rather than calculating minimum surface intervals to cram as much diving time into a diving day. If you want to spend more time in the water, a much better way of doing this is to spend an extended period shallower than 9m at the end of each dive.

During this time, your body will be releasing inert gas accumulated during the deeper part of your dive.

Experiments that monitor the presence of tiny bubbles in divers after diving have shown that this practice reduces a diver’s post-dive bubble-count considerably.

Build buffers into all aspects of your dive-planning and execution. Be thoughtful and develop a defensive mindset along the lines set out here.

You will find that focusing on safety as your priority carries no downside in terms of the quality of your diving.

This article is adapted from Simon Pridmore’s new book:

Scuba Exceptional – Become the Best Diver You Can Be

It’s now available in both paperback and ebook versions via Amazon and other online bookstores worldwide.