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The Scuba Doctor has a great range of quality dive computer solutions for technical and rebreather divers.

Decompression Algorithms: ZHL-16C, VPM-B, DCAP, DCIEM, VVAL-18M... Does It Really Matter?

At the risk of annoying those who do have a preference for a specific decompression algorithm, the simple answer for most divers is NO the algorithm is not critical. There is no expert consensus that any one of the current crop of decompression algorithms is better than another. All of these algorithms used in dive computers and desktop table generation software, when set to their default conservancy values, will get you out of the water with an acceptable margin of safety. What we can say for sure is they are all imperfect representations of actual decompression in humans.

Numerous variants of ZHL-16C are very widely implemented in both sport and technical dive computers. For technical diving, versions of ZHL-16C that include user configurable Gradient Factor modifications are very popular because the GF values can be 'tuned' to provide different types of profiles for specific types of diving. VPM-B dive profiles typically have deeper initial stops, along with reduced time at shallow depths resulting in a 'smoother' profile although recent research calls into question the benefits of 'deep stops' especially for lengthy VPM-B profiles. DCAP was developed for use by early extended range divers (today we call them 'technical divers'.) VVAL-18M is the basis for the modern US Navy Tables. DCIEM has been extensively tested by the Canadian military to ensure its applicability to cold water working divers. RGBM (basis for NAUI tables with its roots in VPM) and DSAT (basis for PADI tables) are most often seen in no stop required sport diving applications. Recently, the RGBM model has been called in to question by a legal action, but it's not clear if the issue is with the algorithm itself or a specific dive computers' implementation, as most experts consider the RGBM model to be very conservative especially on repetitive dives.

The practices of decompression are not exact, in many ways as much about skill as science. Much of what we do in decompression diving is based on empirical observation and experience, rather than having a basis in theoretical science. Dr. R W (Bill) Hamilton, the late co-developer of DCAP and whose research in decompression is widely acknowledged as having a key role in opening up recreational extreme exposure diving in the early 90s, was fond of the saying 'what works, works'. The most important safety factor is not the decompression algorithm you select, rather your skill as a diver and that you closely follow the recommendations of that algorithm and safe diving practices in general. Also, best practice when diving as a team is that all divers should use the same algorithm in order to remain together as a team during ascent phase of the dive plan.



Sydney and NSW Dive Sites

Sydney and NSW Dive Sites

Sydney, NSW, Australia, and NSW generally, has some interesting shore and boat dive sites, most of which are part of the Great Southern Reef which is a more colourful and abundant reef ecosystem than that of the world famous Great Barrier Reef. These resources, put together by the amazing Michael McFadyen, will help you to enjoy them.

Dive Sites

Sydney and NSW Other Dive Information

The best reference book on diving in Sydney and New South Wales is:

Through extensive travelling and diving, authors Graham Willis and Johan Boshoff bring you valuable information on more than 250 dive and snorkelling spots in New South Wales. Guidelines and information on each dive destination include accommodation, facilities, travelling tips and dive conditions.

The best reference book on diving in Australia, inclusive of Sydney and NSW, is:
Dive Australia - A Scuba Divers Handbook (5th Ed) Dive Australia - A Scuba Divers Handbook (5th Ed)
RRP: $58.90, Our Price: $56, You Save $2.90 (5%).
Amongst many other things in this remarkable hardcover book of over a thousand pages you will find:
* 553 mono photographs
* 58 colour photographs over 16 pages
* 60 maps, and over half a million words
* state by state descriptions of over 2000 dive sites including shipwrecks, marine life and general terrain, including the type of diving available, be it from shore, boat or off (and under) a jetty, and any concerns that the diver need be aware of.

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