The most important part of any dive is the ascent. Putting together a safe ascent strategy should be part of every diving plan. One characteristic of this ascent strategy should be how to slow down our ascent and allow for efficient off-gassing of the inert gas that has entered our tissues. This post will discuss deep stops and their benefits.
Before we discuss what deep stops are and how to calculate them, let’s take a quick look at the history of the deep stop. Deep stops were first brought to light by Richard Pyle. This is why deep stops are sometimes referred to as Pyle Stops. Pyle is a ichthyologist. That is, he studies fish for science and describes himself as a fist nerd. Pyle collects all types of fish on deep reefs. Once he has collected them, he had to stop at random depths, before his decompression stops, in order to equalize the fish’s swim bladder so it wouldn’t rupture on the way to the surface. When we was doing these stops, he noticed that he felt much better after those dives when compared to dives in which he didn’t do these stops. He then started to add these stops, deeper than his first deco stops, to all of his dives.
What are Deep Stops?
A deep stop is a pause or a series of pauses on the ascent, prior to any mandatory stops (either safety or deco). My rule of thumb is that whenever I go deeper than 60 feet, I’m doing deep stops. For recreational dives, a deep stop is a 30 second stop at 50% (half) of the maximum depth for the dive. Then after that 30 seconds, you ascend at 10 foot increments taking 30 seconds to travel those 10 feet and stopping for 30 seconds after arriving at the new, shallower depth. For technical dives, the deep stops start at 75% of the maximum depth. Then doing the same 30 second travel and 30 second stop until the first decompression stop. The reason for this is that technical dives incur more gas loading than recreational dives. Below is a picture for a 100 foot recreational dive and the deep and recreational stops.
100 ft Deep Stop Example
In this example, we are doing a 100 foot recreational dive. If we do a 3 minute safety stop at 20, let’s look at our deep stop strategy. We will do our first deep stop at 50 feet for 30 seconds, we then take 30 seconds to travel to 40 feet. At 40 feet we stay for 30 seconds and then travel to 30 feet, taking 30 seconds to get there. We do this until we get to 20 feet. At 20 feet, we will do our mandatory 3 minute safety stop followed by a 3 minute ascent to the surface. We do this slow ascent from 20 feet because air expands much faster the closer we get to the surface. Therefore, we slow down our ascent from 20 feet to the surface.
Why Do We Need Deep Stops for Recreational Dives?
As a recreational starts to do deep dives, gas loading in the tissues becomes much more of a concern than shallow dives. In my previous post, I discuss the differences between the dissolved gas and free phase gas models in decompression theory, Best Practices – Dive Planning Part 3. When we combine deep stops along with our safety stops, we get the best of both worlds. That is, we can address the free phase bubbles and dissolved gas with this ascent combination. This makes for a safer ascent. By adding in deep stops, it forces us to slow down our ascent.
You’re probably saying, “This is great, but aren’t NDL limits created so that we can do a direct ascent, without doing safety stops and NOT get bent?” Many will argue that this may or may not be true. However, when we look at the average recreational diver, we are not in optimum physical fitness, have medical conditions or be on medications that increase our susceptibility to DCS. There are other conditions/reasons, but the point is the average recreational scuba diver is not the optimum specimen for physical fitness. If we have a faster than normal ascent and blow through any safety stops, then the risk of getting hurt can dramatically increase. When we take these physiological items into account, we should try to keep our dives as safe as possible. This includes incorporating deep stops into your ascent profiles.
I have noticed a better, post-dive feeling after doing dives with deep stops. I hope you start to incorporate deep stops into you deeper dives.
Dive Safe,
Duane Johnson
Precision Diving
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About Duane Johnson
