Safety Refresher: Descent, Ascent and Stops

Sometimes a quick review of basics is in order, and after hearing and reading about some avoidable injuries and a death in the diving world, it was time to push out a refresher article. We all learned during basic open water (or the equivalent thereof) diver that controlled descent/ascent and safety stops are a must for every dive, even when you’re still well on the no-decompression side of the dive tables. Unfortunately, people have a tendency to become complacent after numerous safe dives; ascent rates increase, bottom times are pushed to the limits, and computers are depended on more than planning and tables. Unfortunately, while alone, these are bad habits; but together they can equal a minor DCI hit or even a major one. So… let the refresher begin!

Descent Rates:
This is the easy one. Descend as fast as is comfortable for you, frequently clearing your ears and maintaining buoyancy control. While descending, pay attention to your buddy to ensure you both reach bottom around the same time. Remember here: bottom time starts from when you leave the surface to when you leave bottom. So a planned 40 minute dive to 20m would be 40 minutes from leaving the surface to leaving the bottom, about 2 minutes of ascent to a safety stop of 5 minutes at 3m; the total time in the water would be around 48 minutes give or take a bit.

Ascent Rates:
Here’s where I err on the conservative side of caution. DCIEM (now DRDC) produced the best researched and evaluated dive tables released for civilian use back in 1992, after exhaustive and thorough research. While disliked for their conservative numbers, their tables have the lowest margin of error of any tables I am aware of, including USN and RN tables. Why? Because they were designed for divers of multiple ages, both sexes and differing levels of physical fitness as opposed to young, fit, male navy divers. 15m/min +/- 3m is their recommended ascent rate. I stick to 12-15m/minute. I advise the slower rate because the entire process is assisting you in decompressing and regulating the release of nitrogen from your very real theoretical tissues.

Safety Stops:
As I said earlier, 5 minutes at 3m. Even if you’ve had the perfect dive and are well within your tables and it’s your first dive, the extra time spent floating or hanging at 3m will greatly assist your system in decompressing itself. As an extra safety measure, I like to write out my maximum bottom times and deco stops on a slate, not just for my planned depth, but also for two depths deeper. That way, should I blow my tables by dipping deeper and suddenly find myself having gone over the maximum time for my new depth, I know I might have to take a longer stop at 3m or even a deeper stop at 6m. Once at your stop depth, just float and chill out; excessive activity has been thought to help release nitrogen in a less controlled manner, leading to issues, so once you’re at your safety stop, just chill.

The key things to take away here are that safety stops aren’t an irritating waste of time you can ignore because your computer says you’re good. They, along with slow ascent times, make up a large part of your decompression cycle after a dive. They become more important if you are planning to conduct multiple dive in the same day. Air embolisms, DCI hits and more can be avoided by safe diving practices. Plan the dive, dive the plan.

About the author

Graeme is a professional diver, qualified as a PADI and SDI Divemaster, DCBC 40m Unrestricted Commercial Scuba Diver, 30m Restricted Surface Supply diver, and CAUS Scientific Diver Lv.2. Graeme has an Associate Degree of Arts in Environmental Studies, where he focused on archaeology and physical geography, and an Advanced GIS certificate.