Why do Scuba Divers Ascend Slowly?

Each year there are nearly 152,000 open water dive certificates issued. (Source: Scubanomics)  While scuba diving is a popular activity that is appealing to many, it is also an activity that requires proper training to maintain safety.  Each year, approximately 200 people die worldwide as a result of scuba diving accidents. (Source: Diver Mag) Knowing how to dive correctly is essential.

Scuba divers ascend slowly because, if a diver ascends too quickly, they can become seriously ill. Ascending slowly helps to lessen the risk of the diver developing decompression illness and avoid reverse ear squeeze.

While it may seem like fun to give a firm push from where you are diving or to kick quickly to the surface, the result can be debilitating and even life-threatening.  In this article, you will learn why scuba divers ascend slowly to the surface. 

What Happens to Your Body When You Dive? 

Aside from ensuring you have the proper gear for scuba diving, the ascent is one of the most critical parts of scuba diving that does not leave much room for error.  Your body has several physiological reactions when your scuba dive.  Two of the most common ailments experienced by scuba divers are the bends and squeezes.  Each of these occurs when there is an issue with the pressurization of the body. (Source: American Family Physician)


As you dive down, the pressure of the water increases dramatically. The pressure increase depends on whether the water is freshwater or saltwater.  As you descend into the water, the air in your body is significantly compressed.  When you ascend, the air expands. (Source: Abyss Ocean World)  

If you have ever been at the bottom of a swimming pool, you have likely felt the pressure in your ears and lungs.  This pressure is magnified during a dive. The scuba gear you wear helps to offset the pressurization effects on the air you are breathing; however, the changes on your body are still apparent and need to be kept in mind throughout the dive. 

It is also a common misconception that the gear helps your body not to be “crushed” by the water pressure.  This is not true.  The gear helps you to stay warm and protected while monitoring the amount of air and time you have left for your dive. 

Equalize early and often on descent. Ascend slowly to allow air to exit the ears

A couple of dangerous situations that can happen during a dive are:

  • Crushed by water pressure: Descending into the ocean or any body of water for that matter will exert an increased pressure on your body.  As you descend, the pressure increases and forces the air out of your lungs, thereby causing them to cave in. (Source: Sciencing)  This doesn’t occur at recreational scuba diving depths.  This is avoidable by not holding your breath at depth. Your regulator will supply you with the correct volume and pressure of air to prevent this.
  • Squeezes: One common problem that can occur during descent is called a squeeze.  This occurs when the pressure changes and affects both your mask area and inner ears.  There is extreme pain associated with this ailment, but it usually heals on its own with time. Learn to properly equalize on descent, and ascend slowly to allow pressure to decrease before you feel pain.

When the squeezes occur, the pressure causes your face mask to suction against your face.  If you have ever experienced a suction cup on your skin, you likely know how much it pulls at your skin.  The face mask pulls at the skin around your eyes, which can cause bruising to occur.  In a severe situation, blood vessels in your eyes may even be impacted. (Source: Ocean Scuba)

You avoid ear squeezes by equalizing as you descend. You avoid mask squeezes by exhaling a small amount of air through your nose as external pressure builds. If you experience ear pain on ascent, descend to the point where the pain goes away, and try swallowing your saliva a couple of times. You can gently equalize to open your Eustachian tubes, but don’t add much air or you magnify the problem. You can also try rolling sideways to reposition the trapped air.

This is called a reverse squeeze, and it is miserable if you ascend all to the surface without trying to correct it first. Only one of us has ever experienced this, but she felt bad for 24 hours with severe pain for the first 6 hours.

Why is it Vital to Ascend Slowly?

One of the most critical moments during a dive is the ascent to the surface.  This is the part of the dive that requires careful calculation and patience.  If a diver ascends or comes to the surface too quickly, they will face serious consequences, often referred to as the bends. 

  • Bends (decompression sickness): Unlike the name sounds, it has nothing to do with bending or contorting your body.  The bends occur when your lungs over-expand.  Remember, added pressure causes compression of the air in your body while releasing the pressure causes the air in your body to expand. And it doesn’t occur from swimming too soon after eating, moms.

The bends affect many parts of your body.  Typically, when a diver is suffering from the bends, they will notice weakness or numbness in the arms and legs, dizziness, vomiting, or even losing consciousness.  This is a medical condition that needs to be treated by a physician, as it can affect your entire circulatory system, including your heart. (Source: E-Medicine Health)

How Do You Ascend Safely?

When a diver begins their ascent, it needs to be carefully planned and executed.  It is recommended that an ascent take place in two different stages that are carefully timed and monitored by the diver.

Stage 1 of the Ascent (Decompression Stop)During this stage of the ascent, the goal of the diver is to reach a safe ascent zone.  This means they are ascending from a deep dive location and will need to stabilize halfway to the surface. This decompression stop allows the body to reacclimate to the changing pressure gradually. It is recommended that a diver not ascend more quickly than 30 feet per minute. (Source: Scuba Diving) If you have been on an extremely deep dive, you may have more than one stopping point before reaching the surface. 
Stage 2 of the AscentThis is the final stage of the ascent and a time to be extra cautious.  It may be tempting to rush to the surface when you can see it just above you; however, you need to continue a slow and steady ascent. It is crucial to slowly release air pressure during this final phase of the ascent to ensure you are correctly depressurizing. 

(Source: Dive Training Magazine)

How Do You Track Your Ascent?

Most scuba divers use a dive computer to track their dive times and frequency and decompression status. The dive computer provides the diver with information regarding the time left for a safe dive as well as the depth they have reached.

Determination of safety stops, time between dives, time spent at each depth, required surface break, and more are tracked. (Source: Oyster Diving) The safety of your ascent will be dependent upon the tools you use as well as the communication you have with your dive partner. Your depth gauge and dive watch or computer are used in tandem. If you aren’t using a computer, then you will rely on manual dive tables to track these things.

The entire time a diver is making the ascent to the surface, they should consult their dive computer as well as their diving partner to ensure they are ascending at a safe rate and leaving enough time for the dive to be completed safely.  There are many dive computers on the market, and a dive instructor will likely be able to recommend the best option for you.  

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However, if you are looking to purchase without consultation, here are some options:

Each of these options has fantastic reviews, but if you are uncertain about the brand, style, or type, it would be recommended to seek the help of a professional diver. When purchasing a dive computer, you can plan to spend between $200 – $1,500.  Do not fall into the trap of thinking more expensive is better because that may not always be the case.  Instead, enlist the help of a professional to guide you. 

Why Can Snorkelers Ascend Quickly?

Snorkeling is much different than scuba diving because it involves swimming at the surface of the water.  They inhale air at surface pressure, so when they ascend, there is no expansion as pressure decreases. Therefore, snorkelers do not need to worry about the speed of their ascent.  They are not deep enough in the water to experience the pressure difference that a scuba diver does. (Source: Leisure Pro)

Final Thoughts

Scuba diving is a favorite activity for many people around the world.  While fun and exciting, it requires thorough training to execute a safe and successful dive.  The two bookends to a successful dive are the descent and ascent.  By following safety precautions and ascending slowly with dive stops along the way, you will ensure an enjoyable – and safe – dive. 

Tim Conner, M.D.

Tim Conner, M.D. started boating in 1974. He has been involved in recreational boating continuously since then. Dr. Conner has been active in boating and watersports safety education for decades. He rode his first jet ski in 1997, and rejoined the personal watercraft arena in 2012 with a Sea-Doo GTX 155, followed by 2 supercharged SeaDoos. Scuba certification came in 1988, and he and the family have traveled the world snorkeling and scuba diving for decades. The family has recently taken up paddle boarding. Click the photo for a lot more.

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