In Praise of the Humble Safety Stop

Scuba diver looking at wrist gauge

Safety stops are a critical part of scuba diving safety. We all learned about them in our Open Water Diver course. The concept was reviewed and reinforced in every course after that. Yet I can’t help but feel most divers don’t truly appreciate the importance of the humble safety stop. Let’s take a look at how safety stops reduce risk and why they are so important.

Let’s quickly review what happens in our bodies during a dive. When you breathe compressed air underwater, nitrogen dissolves into your blood and tissues and begins to accumulate. As you ascend, the pressure decreases and the accumulated nitrogen is transported back to the lungs and eliminated. If you ascend too quickly, the nitrogen can form bubbles in the blood vessels and tissues. These bubbles can cause pain, numbness, and other symptoms of decompression sickness. Safety stops help to reduce the risk of decompression sickness by allowing your body to off-gas the nitrogen it has accumulated during the dive more slowly.

There are several benefits to making a safety stop at the end of every dive:

  • Reduces the risk of decompression sickness. This is the most important benefit of safety stops. By off-gassing the nitrogen slowly, safety stops help to prevent the formation of nitrogen bubbles in the bloodstream and tissues. This is especially important for deep dives and dives that involve a lot of time at depth.
  • Improves buoyancy control. The greatest pressure change in scuba diving occurs near the surface. This can make it difficult to control buoyancy and maintain a safe ascent rate. Safety stops give you a chance to fine-tune your buoyancy and practice slow, controlled ascents. This can help to prevent shallow water blackouts, which can occur when you ascend too quickly and causes you to lose consciousness.
  • Allows the diver to check their equipment. Safety stops provide a good opportunity for you to check your equipment and make sure everything is in good working order. This is especially important after a long dive, when equipment may be starting to show signs of wear and tear.
  • Allows the diver to assess the surface conditions. Before surfacing, it is important to assess the surface conditions and make sure it is safe to ascend. Safety stops give you a chance to do this and avoid any potential hazards, such as boat traffic.

Research Summary

That sounds like good advice, but still need proof? In a study conducted at the University of North Carolina at Wilmington,1 researchers tested three groups of divers who all did the same no-stop dive profile. The first group ascended directly to the surface at the proper ascent rate, but did not perform a safety stop. The second group ascended at the prescribed ascent rate and did a 2 minute safety stop at 10 feet. The third group also ascended at a normal rate but did a 1 minute stop at 20 feet and a 4 minute stop at 10 feet. All divers were checked with a Doppler ultrasound device upon surfacing and every 15 minutes thereafter. There were no cases of Decompression Sickness (DCS). The Doppler testing did track “silent bubbles” in each diver.

The first group (direct ascent) showed a significant number of silent bubbles upon surfacing. The number of bubbles greatly increased after 15 minutes. The number of bubbles then slowly declined. There was still a significant number of bubbles after two hours. The second group (2 min at 10′) showed a remarkable reduction in the number of bubbles present compared to the first group. The third group (1 min at 20′ and 4 min at 10′) showed an even lower number of bubbles. In fact, Group 3 had fewer bubbles upon surfacing than Group 1 divers after two hours on the surface. And, Group 3 divers showed no bubbles at all after 45 minutes at the surface. This graph summarizes the results.2

Graph showing reduced bubbles after safety stop


The implications of this study are astounding. By adding even a brief safety stop, the number of silent bubbles present after a dive are greatly reduced. Also consider repetitive dives. If conducting a second dive after a one hour surface interval, divers in Group 3 are starting with no bubbles while divers in Group 1 are starting the dive with a large amount of bubbles already present.

This information should make it clear why safety stops are recommended for all dives, regardless of depth or duration. They are especially important for deep dives and dives that involve a lot of time at depth.

Here are some tips for making safety stops:

  • Make the safety stop at a depth of 15-20 feet.
  • Stay at the safety stop for at least three minutes.
  • Relax and breathe slowly.
  • Monitor your buoyancy and ascent rate.
  • Check your equipment.
  • Assess the surface conditions.

Safety stops are a simple and effective way to reduce the risk of decompression sickness and other diving-related injuries. Hopefully after reading this article, you will make safety stops part of your diving routine on every dive.

  1. Ugucionni, 1994 ↩︎
  2. Powell, Mark, Deco for Divers Second Edition, 2014, Aquapress, LTD ↩︎