You have done your Open Water course & your Advanced Open Water – what’s next? While I am not a fan of getting certifications just for certification’s sake (there is a post about that on the horizon…) there are plenty of cool scuba courses out there to further your skills even if you are not wanting to go pro.
These courses are called specialties and all scuba agencies offer them. Your AOW will most likely have given you a first glimpse into what else is out there. Depending on your interests and diving conditions you can do courses like navigation, fish ID, ice diving, drift diving, and many more. The course catalog is still growing and chances are you will find something that will tickle your fancy.
However, there are a few courses that are not only interesting but also incredibly useful, and the skills you will learn apply to most of your future dives. One of those is the Deep Diver Speciality.
What is the Deep Diver Course

In recreational diving, we define a deep dive as any dive below 18 m. If you have at least an Open Water chances are, you have already done your first deep dive when your instructor took you to 18 m. Once you have your Advanced you will probably do deep dives on a regular basis.
A recreational deep dive happens between 18 m and 40 m depth.
One of the prerequisites to get your Advanced Open Water is one deep dive and as you know, once you are certified you are allowed to dive to 30 m with your buddy. During your deep dive your instructor will have spoken to you about dive planning, the effects of pressure at depth, what happens to colors at depth, and nitrogen narcosis.
Mind you, this is just one dive. During your specialty course, you will dive deeper, figuratively and literally. You will learn more about how pressure affects the body and breathing the deeper you dive, how the partial pressure of nitrogen will cause nitrogen narcosis and increase the risk of decompression sickness, what equipment is needed for deep dives, and how to plan a deep dive safely.
Especially the latter is incredibly important as you will need to know how your air consumption increases at depth and how to plan your dive so you always have enough air to come up safely from depth. During your dives, you may also learn how to use an alternate air source and/or place a drop-tank for your safety stop.
Afterward, your instructor will take you diving below 30 m to put all the theoretical knowledge into practice. Once you are a certified Deep Diver you are even allowed to dive to 40 m – how exciting!
Why you should get your Deep Diver
Depending on how long you have been diving, the Deep Diver specialty can be a great course to take. It is especially useful when it comes to dive planning, monitoring your air consumption and buoyancy as well as practicing safety procedures. It will also make you more aware of the effects of nitrogen narcosis how to spot them and what to do when it happens.
Mind you, most of this is something you can do above 30 m. I am not a huge fan of diving deep unless there is a good reason for it. No need to shorten a dive thanks to tight NDLs (no-decompression limits) and increased air consumption at depth, and to put more strain on my body than absolutely necessary. That said, some dive sites will require you to go a bit deeper, and in the recreational dive world that is usually a cool wreck. While a lot of recreational wrecks are accessible with Advanced Open Water, some parts of a wreck can lay deeper.
In addition, doing a Deep Diver course was a matter of safety for me. Unlike common belief, you are not allowed to dive deeper than 30 m unless you are a certified deep diver. For the longest time I thought having done my AOW and then divemaster I would be fine diving below 30 m (including some instructors misinforming me about it) but that is not true. All scuba agencies require you to have a Deep Diver certification to go below 30 m. And while you may be perfectly fine handling yourself at depth if you have enough dives under your belt, your insurance will not cover you if you dive below your certification. So even if you just dip to 31 m by accident (looking at you albino moray eel!) your insurance will not help should anything happen to you on the way up. Make no mistake, an accident doesn’t have to happen at depth but might as well happen on the way up – your insurance is unlikely going to cover you when they check your computer and see that you have gone beyond your limit.
So while it may only be a formality if you are already advanced in your dive training, the Deep Diver is a really useful certification to have.
Prerequisites for the Deep Diving specialty

The prerequisites to start your Deep Diver course will very much depend on the agency you choose. Here is a little overview for PADI, SSI, and SDI:
PADI Deep Diver:
Includes 4 open water dives
Minimum 15 years
Must have an Adventure Diver or Advanced Open Water certification to do the PADI Deep Dive specialty
SSI Deep Diver:
Includes 3 open water dives
Minimum 15 years
SDI Deep Diver:
Includes 2 open water dives
Minimum 18 years, 10 years with parental consent
Must have an SDI Open Water Scuba Diver (or Junior Open Water) or equivalent
In addition to the open water dives, you will also have to do some academics and a short quiz. Mind you, the materials are easy to comprehend, and compared to your OW or other courses there isn’t too much studying involved.
SDI Deep Diver with Big Blue
As you may know by now, I am not tied to one agency but think it is more important to find the right instructor for you. This was the reason why I started to get some SDI certifications in recent years, an agency I hadn’t even heard of when I started diving.
After a long search for a great instructor and dive center in Koh Tao, I ended up with Fiona at Big Blue Diving. She is also part of their technical division, Big Blue Tech, and an all-around amazing person and teacher. After having done my Solo Diver with her in 2018 I knew I was going to come back to her for future training.
When we looked at the courses I wanted to do she was the one who suggested the SDI Deep Diver. This way I wouldn’t have to worry about depth limits in the future (and worry about insurance coverage) and could move on to wreck diving after without being limited to 30 m.
When planning a deep dive you not only need to consider your shorter NDLs but also your increased air consumption. For an air-hog like myself, my air dictates my dive time, not my NDLs. Therefore Fiona and I decided that I would do my Deep Diver specialty on a twinset.
Interestingly enough diving with twinset (aka two connected tanks on your back) doesn’t require its own special course, unlike Sidemount. But it definitely takes a few dives to get used to the setup, learn how to separate the air in the tanks in case of emergency, and moving around under the surface and above with a lot of extra weight on your back. I welcomed the chance to learn all this from a great instructor while enjoying the bonus of having air from 2 tanks!
We did a total of 4 dives during the course. The deepest dive at Chip-Ship off Koh Tao took me to 37 m and it was probably the first time in my life that my dive was cut short by my NDL and not by my remaining air.
Chances are you have an idea of why you want to get your Deep Diver and what you want to learn during your course. I recommend chatting with potential instructors and see what they offer and how they structure their courses.
My SDI Deep Diver course included 4 open water dives instead of the required 2 as well as twinset training and equipment. It was slightly more expensive than the average course but so worth it. Ultimately I wasn’t keen to pay for a certification purely for insurance purposes or to have an instructor show me what pressure at depth does to a packet of chips – I really wanted to learn something new and improve my dive skills which is exactly what I got from my course and Fiona!