Deep diving can be an emotive subject in the diving circles, to some the maximum depth a diver has attained is an overriding factor in a divers skill and competence. While the practice of 'Bounce Diving' (A very fast descent on an air mix to a target depth of 60 M+ then immediately ascending) is a known method of deep diving for the most part a divers skill is not proportional to the depth reached. Certainly a different way of gauging a divers skill would be a diver carrying out a pre-planned technical dive to a deep depth then carrying out exploration and other work while submerged. Of course diving is an adventurous sport and one way of achieving that adventure is to dive deep purely for the sake and challenge of going deeper than before. For others diving as much of the ocean as possible and penetrating deeply will explore a little more of the underwater realm.
Deep diving is accompanied by extra dangers and the desire for pushing the limits should be tempered by the need for caution.
Risks of Deep Diving
Although diving is arguably considered a risky undertaking it should be made crystal clear that deep diving up to and beyond recreational limits brings with it increased risk and hazards.
Having said all this divers choosing to expose themselves to these risk can benefit from discovering new dive sites, shipwrecks and certain marine life may only be found at certain depths. The adventure and enjoyment in doing this can be immense as well as that some divers thrive on the challenge and dangers faced.
Categories of Deep Diving
It is important to keep in mind that deep diving is not for anyone, no matter how long someone has been diving. A veteran diver of the shallow reefs should feel no shame in having not ventured deeper into the underwater depths. It is useful, however, to categorize deep dives by depth bands.
30 - 40 Meters
Increased care and experience is required for most dives. Nervous and unskilled divers should think carefully before committing to entering this region. Experienced divers should now become more aware, both of themselves and their buddy.
40 - 50 Meters
This is the kind of diving that should only be undertaken by divers experienced in deep diving and aware of the risks. Air consumption, narcosis and the chill factor all become heavily apparent now. These depths are for dive-fit divers with the appropriate back-ups and water conditions.
50 Meters +
Recreational divers should not undertake dives to these depths. Air consumption and narcosis loading are now at levels only technical divers should consider. Oxygen toxicity is now a distinct possibility and air / gas mixes are consumed at over treble the level than that at 10 meters. Diving in this region requires a very high level of competence, aptitude, equipment and experience. It is therefore considered the domain of the very few.
The above categories and comments apply mainly to temperate waters and in warmer waters / tropics some of the deeper diving constraints are reduced, thus allowing deeper depths to be reached.
Personal Equipment - Deep Diving
The deep diver must be thoroughly familiar with his personal equipment. He needs to be able to put his hand on his direct-feed inflator, for instance, without hesitation. Many problems on deep dives are casued by divers using unfamiliar equipment acquired just for the dive, thus causing problems with buoyancy and ill-fitting harnesses. Ideally all your diving equipment needs to be comfortable and unlikely to be an annoyance, as due to possible decompression requirements you will be wearing it a lot longer than normal. A prime example of this is the wearing of a thicker wetsuit than normal to combat heat loss to the wearing of a dry suit.
A totally adequate air supply is essential for deep diving. The majority of incidents are caused by an inadequate supply of air, often resulting in too rapid ascents. It is an excellent idea to plan to end the dive with a reserve of about one third of your air remaining. This air can also be useful on the surface when there is a swell.
Most deep diving incorporates decompression stops to ensure safe off-gassing of nitrogen from the body tissues. Many divers who dive deep use a high blend oxygen blend of nitrox as a decompression gas. This is because of the reduced amount of nitrogen in the mix, which ensures a more enhanced decompression than using air. Some divers carry 100% O2 cylinders for maximum decompression effects although only fully qualified tech divers are normally allowed to do this.
Buoyancy loss need not be a problem with the use of direct-feed inflators. However, it is important that divers are aware of buoyancy loss and compensate during their descent rather than waiting until the target depth and being at maximum buoyancy loss. The total buoyancy loss at 30 meters can be up to 10 kilos when wearing a wetsuit.
Instruments and Accessories
It is vital that depth and time are accurately recorded on every dive. On deep dives the inaccurate recording of times and depths has led to many decompression and other incidents. Consequently, instruments must be regularly checked for accuracy and have bold, luminous faces. At depth, with the problems of narcosis and poor light conditions, they must be clearly readably.