Scuba diving is a relaxing activity enjoyed by many people. It is also very safe. So why would some people be feeling sick after scuba diving? What are the causes of feeling a bit ill, and what is the difference between feeling sick after scuba diving vs. having a scuba diving illness such as decompression sickness?

Feeling Sick after Scuba Diving

Feeling sick after scuba diving can be quite common. Let’s first have a look at the minor sicknesses that can be brought on by scuba diving.


If I had a dollar for every dehydrated student I’ve had, I would have about 500 dollars! Every week we will have a student feeling ill after the dives, and most times it is mild dehydration. Common symptoms include; dizziness, tiredness, and difficulty breathing. In severe cases, I have seen students cramp up and lose feeling in their extremities; where they can’t move their fingers or toes. The symptoms can be very similar to Decompression Sickness (we will go talk about this further in this article) so the best way to avoid this is to drink lots of water and electrolytes before and after the dives. Avoid tea, coffee, and alcohol.


If you are not used to being on a boat, you may experience seasickness. This can range from mild (feeling a bit dizzy), to severe (non-stop throwing up/vomiting). The best place when you are feeling seasick is to get into the water as soon as possible. Believe me! Motion sickness is caused by your brain and your inner ear (which controls balance) and your eyes telling you two different things; for example, on the boat, you feel stable, but your eyes are telling you that you are moving. When you get into the water, you will be moving with the water and feeling the movement of the water which stops the seasickness.

The motion sickness can return when you get back onto the boat, and even for a while when you get back on-land. The best way to avoid this is to take non-drowsy motion sickness medication before getting on the boat, staying hydrated with water, and sitting in the middle of the boat (the most stable section) and looking out to the horizon.


It is normal to feel a bit nervous before your dives, especially if it is your first dive in the open water. This may cause you to feel a bit dizzy and nauseous before, during, and after your dives. You may feel butterflies in your stomach and feel the need to throw up or use the toilet. The most important thing here is to remember to breathe and try to relax.

Food Poisoning

Most people will scuba dive for the first time on their tropical holidays. This is why the largest concentration of dive shops and certifications are in holiday destinations. So if you are overseas, you might be eating new and exotic food. Food that may not necessarily sit well with your stomach. Try to avoid spicy curries, seafood, greasy food, and questionable meat before your dives.

Physical Exercise

Diving might not seem it, but it is a physical activity and you will be burning calories! Moving tanks, weights, putting on the heavy equipment, engaging your core muscles to get into the right diving position underwater and getting back onto the boat are things that can cause you to sweat. If you are not used to exercising, you may feel it is physically strenuous and this can make you feel sick (think about the first time back at the gym!). Remember to hydrate and take it easy, especially under the blazing sun or in a hot drysuit.

Mental Exercise

Getting your Open Water certification is almost like going back to school! There are physics and dive theory to learn, new skills to get your head around, and exams!! Luckily, it’s not too difficult and quite repetitive (remember the course is open to 10-year-olds too). But learning something new and mentally stimulating your brain can be quite tiring. This can learn to some headaches, dizziness, and even nausea. Take it easy and talk to your Dive Instructor about slowing down the course and doing it in more sizable chunks.

Moving in a 3 Dimensional Space

It’s just the unbelievable fact that you can move in three dimensions.”

Sir David Attenborough

As Sir David Attenborough mentioned, being able to move in three dimensions; forwards / backwards, left / right, and up / down is an amazing and unbelievable notion. This is something that we cannot experience on land without electronics. Because we are not used to this motion, sometimes people can experience vertigo which leads to dizziness and nausea. If you are experiencing vertigo underwater, try closing your eyes to steady the spinning. You could also hold onto your buddy or a descent line. If you are still feeling sick after scuba diving, then lay down and rest for a while.

What is Decompression Sickness

Decompression sickness is caused when the nitrogen that you absorb during a dive forms bubbles in your blood and tissues as the pressure decreases (when you ascend). The biggest cause of this is ascending too fast, or spending too long at a certain depth and absorbing too much nitrogen. Other factors that increase the risk of decompression sickness (DCS) include but are not limited to; fatigue, excessive body fat, dehydration, older agee, and certain existing heart defects, such as a patent foramen ovale (PFO).

First Aid for suspected DCS is 100% oxygen on the boat or on-land. In severe cases, you may need to go into a recompression chamber or hyperbaric treatment chamber to simulate pressure for the nitrogen in your tissues to dissolve again.

Mild Decompression Sickness Symptoms

  • Dizziness
  • Headache
  • Confusion
  • Extreme fatigue
  • Tingling or numbness in arms or legs
  • Joint pain
  • Weakness in arms or legs

As you can see, some of these symptoms can overlap with other causes of sickness after scuba diving. This is why it is important to ensure you are fit to dive, hydrated, well-rested, and ready for a scuba dive. This will reduce the risk of feeling sick after scuba diving, and will also reduce the likelihood of DCS.


There are many reasons to be feeling sick after scuba diving. Hopefully, it is not a lasting feeling, and most causes of sickness can be explained by mild factors such as nerves or seasickness. Of course, there is the risk that your symptoms may be DCS but this is rare if you follow the basic scuba diving rules. The main thing to remember when scuba diving is to relax, breathe, and take it easy. No wonder we call it the ‘lazy sport!’