Deep Diving: Rules, Recommendations And Fun Facts

Deep Diving: Rules, Recommendations And Fun Facts
Jon Milnes

How deep do you dive?

It’s often the first question a diver gets.

And what is the real answer to that question?

Have you been diving at a reef edge or a vertical wall where you see life at greater depths? Do you want to go deeper, but your training and experience limits you?

Here are some facts that you need to know about deep diving.

What is Deep Diving?

Deep Diving is any dive deeper than 20 meters (60 feet). However there are different kinds of diving which gives deep diving its own specific definition. In Recreational diving, the maximum depth limit is 40 meters (130 feet).

In technical diving, a dive deeper than 60 meters (200 feet) is described as a deep dive.

However, as defined by most recreational diving agencies, a deep dive allows you to descend to 18 meters and beyond.

Decending to the Wreck
Decending to the Wreck
Photo by: Jon Milnes

Risks in Deep Diving

Deep diving is relatively safe as long as you follow all the rules and procedures. However, it is important that you know the inherent risk of diving at greater depths.

Decompression Sickness (also called the bends)

When you dive, you breathe in air which is composed of oxygen, nitrogen and other gases. Your body uses the oxygen but nitrogen is eventually released over time since our body does not need it.

So, when pressure suddenly drops, like in the case of a rapid ascent, nitrogen gas inside your body expands and develops into bubbles. These bubbles are usually trapped in the joints causing severe pain. A diver with decompression sickness is treated using hyperbaric oxygen therapy inside a recompression chamber.

Read more about Decompression Sickness and How to Treat it

Jon Milnes

Nitrogen Narcosis

You will experience a narcotic effect when you accumulate too much nitrogen. The first symptoms are tingling of the fingers, dizziness and disorientation. It also affects your sight by experiencing a tunnel vision which makes reading gauges and instruments difficult. The deeper you go, the greater the effect of nitrogen narcosis is.

Rapid Air Consumption

The air you breathe will become denser as you go deeper due to increasing pressure. Meaning, you consume more air while deep diving as compared to diving at shallower depths. So it is highly recommended that you constantly monitor your pressure gauge.

You can also bring an additional small cylinder or a pony bottle, some stage a decompression tank at the safety stop line.


Rules, Recommendations and Tips for a Safe Deep Dive


  1. Plan your dive. Establish your maximum depth and bottom time.
  2. Always perform the Pre-Dive Safety Check before diving.
  3. Regularly monitor your depth and pressure gauge. Make sure that you have plenty of air in your tank for your ascent.


  1. Do not plan your dive so that it exceeds the No Decompression Limits of the dive table.
  2. Never dive alone and always have an experienced buddy with you.
  3. Never go beyond your planned depth nor exceed your bottom time.

How to Get Started

Your first deep dive should be under the supervision of a dive instructor. You can do this during your Advanced Open Water Diver course. You will be trained to dive to a depth of 30 meters (100 feet). You may also have the option to enroll in a Deep Diver Specialty course wherein you will be trained to dive as deep as 40 meters (140 feet).

After your certification, you may plan to go deep diving with an experienced dive buddy. Some deep diving sites may take you to shipwrecks or may require you to use an enriched air to extend your dive time. So you may also consider enrolling in other specialty courses like wreck diving, peak performance buoyancy and enriched air diver.

Dive as it’s any other dive

    1. Get in the water and set your dive watch and establish orientation or direction using your compass.
    2. Once ready, signal your buddy to start descending and slowly deflate your BCD.
    3. You should descend closely together until you reach your planned depth. Watch your buddy for signs of Nitrogen Narcosis.
    4. While descending, you may feel a sudden change of temperature called the thermocline. Just continue with your dive as this occurs naturally.
    5. Never go beyond your planned depth nor exceed your bottom time.
    6. Regularly monitor your depth and pressure gauge. Make sure that you have plenty of air in your tank for your ascent.
    7. Before you start ascending, signal your buddy and you should always ascend together.
    8. Make sure that you deflate your BCD when ascending to prevent rapid ascent.
    9. Ascend slowly and strictly follow the normal ascent rate no faster than 20 meter (60 feet) per minute.
    10. Make sure to do a safety stop at 5 meters (15 feet) for 3 minutes. Deploy your DSMB before your last ascent.

Some of the World’s Famous Sites for Deep Diving

Lighthouse Reef Blue Hole (Belize, Caribbean Sea) – this site was created from an ancient cave system. It almost has a perfect blue circle measuring 300 meters (1,000 feet) in diameter. You can enter an underwater cave where you will be amazed by the amazing stalactite formation. You can also reach a deep coral reef that starts at 33 meters (110 feet) and slopes down to 135 meters (450 feet).

View of the Blue Hole in Belize
View of the Blue Hole in Belize
Photo by: Wata51

Blue Hole (Dahab, Egypt, Red Sea) – known as one of the world’s most dangerous dive sites due to the number of lives it had claimed.

You start your dive by descending through a vertical hollow space in between coral mounds. You will exit through at 27 meters (90 feet) in clear water where you will find a vertical wall. This wall plunges further down to profound depths.

Downside Look of Blue Hole, Egypt
Downside Look of Blue Hole, Egypt
Photo by: Kristina Vackova

Blue Corner Wall (Palau, Micronesia) – You will definitely enjoy this vertical drop-off that starts at 10 meters (30 feet) and plunges down to over 330 meter (1,000 feet) deep. You will find large schools of fish, sharks, turtles, giant groupers, barracudas and many more. Blue corner wall is considered as one of the best dive spot in the world.

Deep diving sites are not only confined in saltwater environments. The Eagle’s Nest Sinkhole in Weeki Wachee, Florida is a freshwater pond. Underneath lays a large chamber with crystal clear water. You start your descent by entering a chamber that leads to the “Main Ballroom”. This is a very large and deep cavern that plunges up to 91 meters (300 feet) deep. Eagle’s Nest is considered as the Mount Everest of Diving and one of the world’s complex dive sites.

World’s Deep Diving record

With the purpose of connecting an underwater pipeline, a team of commercial divers reached a depth of 534 meters (1,752 feet). They used a specially-mixed breathing gas for this job. This happened in 1988 off the coast of the Mediterranean Sea.

The deepest scuba dive was recorded at 332.35 meters (1090.45 feet). This was performed in 2014 in by Egyptian diver Ahmed Abdel Gabr. This dive was declared as the Guinness World Record for Mankind’s Deepest Dive.

The world’s deepest wreck dive was recorded at 205 meters (676 feet) while diving in the Yolanda Wreck in Egypt. This was performed in 2005 by Leigh Cunningham and Mark Andrews.

Do you deep dive?

There’s big difference in what diver like? Some like the shallow dives as other want to go deep. What do you prefer?


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Hi! I’m writing a book and I would need information about diving tips to a 30m depth. Thank you!


Hi Heidi,

Hopefully you will be carrying adequate gas and redundancy when carrying out that planned dive. I have done a quick check of that planned dive using air as both your bottom gas and deco gas with Gradiant Factors 50/85 and got the following:

40m: 18 minutes on the bottom and 2 minutes to descend.
15m: 1 minute taking 2 minutes to ascend to this point.
12m: 1 minute
9m: 2 minutes
6m: 14 minutes

Total Gas required: 2389 Litres and using the rule of thirds mean you plan for 3583.5 Litres. Assuming 230 bar fills this would need a 15.5 Litre cylinder meaning either a 15L with a 3L pony or twin 10s to safely carry out the dive.

To make the dive safer I would recommend carying a stage containing 50% Nitrox so that you can decompress quicker.

Hope you enjoy the course and it teaches adequate gas planning for the dive your are doing.


Thanks for the marvellous informational article.


The definition of a deep recreational dive is typically ‘deeper than 18m/60ft’, but this depends on the training agency. The largest agencies use 18m/60ft.

The maximum depth limit for recreational diving is also training agency dependant. Again, for the largest agencies, it is 40m/130ft. BSAC and CMAS allow dives to 50m, with non-accelerated decompression stops, as part of their recreational syllabus.
In technical diving, there is no definition of a ‘deep dive’. Extended Range level is 50-55m (dependant on agency). This limit exists due to issues with oxygen toxity. Beyond this level, helium is added to breathing gas to offset oxygen toxicity issues, as well as narcosis.

Nitrogen bubbles are not “usually trapped in the joints”, but rather, the symptom of pain-only (type I DCI) is felt radiating from joints due to nerve compression. Like sciatica, the localization of pain does not necessarily occur at the area of damage. For recreational divers, bubbles are often located in, or close by, major blood supplies. That also means they are often located in proximity to major nerves.
Divers are not treated with Hyperbaric Oxygen Therapy (HBOT), as this term describes a different treatment, specific for other ailements;; such as burns or some diseases. DCI treatment is run to specific schedule (table) of recompression/decompression in a hyperbaric chamber, in combination with breathing oxygen to accelerate off-gassing and critial bubble collapse, rehydration through drip and immune-suppresent/anti-coagulant drugs.

Nitrogen narcosis is not caused by the volume of saturated nitrogen, but rather the relative pressure of the nitrogen. In particular, it is linked with high nitrogen partial pressure in the lipid (fatty) cells of the brain, where it is believed to inhibit mental processes in an anasthetic process.
Strictly speaking, a tank left at safety stop depth cannot be described as a ‘decompression tank’ as it’s purpose is not for planned decompression. They are, more generally, called a ‘safety’ or ‘drop’ tank… and allow low-on-air divers to complete their recommended safety stops in comfort. As an emergency resource, they also allow emergency stops to be completed if the diver over-stays their planned dive times at depth.

The Advanced Open Water course does not ‘train’ to 30m/100ft. The deep dive conducted on that course increases diver experience and fulfills agency advice regarding the RECOMMENDATION for “newly certified Open Water divers” to limit their dives to 18m/60ft. There is no specific deep dive training or new skills on the AOW course, so it can neither train nor qualify you for deeper depths. Also, as mentioned in the article, a deep dive is any dive below 18m/60ft… the AOW deep dive does not have to be to 30m/100ft… and thus, the qualification cannot ‘train’ you to that depth. Divers are limited by their training and experience… if they only did a 19m deep dive on AOW, then that is the limit of their training and experience…

Deflating your BCD on ascent is possibly confusing. The diver should retain neutral buoyancy throughout the dive. On ascent, that means expelling excess air as it expands. “Deflating the BCD”gives the impression that the diver should EMPTY their BCD… and ascend negatively buoyant. This jeapordised safety and can cause a more significant buoyancy problem when they reach safety stop and then need to add air to get neutral again.

There is no “deep coral reef” in the Belize Blue Hole. It is a sheer wall, that becomes an underhang at approx 44m. Stalactites descend from that underhang… to a depth of 55 – 60m. The bottom is well below that, under sheer walls, no slope. Local diving operations routinely take under-qualified recreational divers below their maximum depths to see the stalacties. It is a very dangerous practice.

The world records for the deepest, and deepest wreck, dives have both been superceeded. The records stated in the article are many years out of date.

Tony H
Tony H

Hi and thanks for the answer. I know, and like, the deal with shallow diving, especially for shooting pictures, still I want to go deep :-9

Your answer was very helpful. I think I’ll start out by doing the one at 100 ft and see if I need more right away. I’m going to Egypt in a few month and thinking of doing it there. I heard good about a scuba school there.

David Tillotson
David Tillotson

I am not certified beyond 30 metres as yet. I am concentrating on getting my in-water skills honed before taking it any further. Once I feel as comfortable at 25m as I am at 10m, then I’ll consider moving to a deeper level. The issue that then comes up is whether to go to OC trimix or CCR (I don’t think “deep air” is a good idea for me – I don’t get the happy brand of narcosis!)

Torben Lonne
Torben Lonne

Hi Tony,
It’s very good to hear that you are doing your deep training before exploring the depths.
Personally I’m a big fan of shallow diving, the color and light is my favorite, that said I can see what draws with the deep water. Just make sure you don’t exceed your personal limits in the hunt for deep diving.

To answer your question: You can do the Deep specialty right after your advanced, I would say it’s a good idea with some experience before venturing down to 40 meters (130 ft) but if you already have that and you feel that you are ready I would say go for it.
You could also do the advanced deep first, and if you are up for more do the 40 m(130 ft) specialty.

Hope it helped.

Torben Lonne
Torben Lonne

Hi David,
Wow that was a great mistake I made. No the air in the tank shouldn’t get any denser as we descend down. Thanks it’s already corrected!

I really agree, it shouldn’t be about going deep for the sake of going deep. Going on a deep dive increases the risks, which can be okay if you stick to your training and experience, but there should be a reason to go deeper and not just because we can. Well said David, are you deep certified?

David Tillotson
David Tillotson

“The air in your tank will become denser as you go deeper”
This isn’t quite correct (as your tank shouldn’t be changing size), it is the air in your lungs that becomes more dense.
Apart from that minor error, there’s some good advise there. IMHO it’s vital that we understand the risks before progressing our depths, and not just race deeper “because we can”

Tony H
Tony H

Ah I have a an idea of doing the deep in my advanced and then afterwards do the deep specialty. Is it a good idea to do it right after or should I wait and do it when I have a bit more experience?

I know there’s a lot of stuff to see at 60 ft but I’m drawn to the deep 🙂 he
It’s been an idea for some time so it’s nice to know a bit more, thanks for a great guide!

Joel M
Joel M
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As a newly AOWD, I find this article very helpful. I think I need to dive for some time before moving on to deep diving. But it is very intrigued, reading this article. Thank you.

Jimmy Luganje Safari
Jimmy Luganje Safari
Reply to 

I’m just get to learn some new things to you buddies although I choose recreational dive and now I’m almost finishing my Rescue course and i hope to continue go up in exploring world of diving so any changes can come on future.Thanks

Reply to 


Thanks so much for this!

Torben Lonne
Torben Lonne
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