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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.



The Ledges

Reef Dive Reef Dive | Boat access Boat access

Abalone Dive Site Crayfish Dive Site Open Water Rated Outside Port Phillip Reef Dive Site

Depth: 12 m (39 ft) to 16 m (52 ft)

Level: Open Water and beyond.

The Ledges lies off Collendina on the Barwon Coast, east of Ocean Grove and west of Point Lonsdale in Bass Strait. It features an awesome reef structure in 16 metres of water with triple-decker ledges and swim throughs.

This area is not affected by current, but as with all dives close inshore it can be affected by surge.

Bass Strait Warning: Always keep an eye on sea conditions throughout any shore or boat dive in Bass Strait on Victoria's coastline. Please read the warnings on the web page diving-in-bass-strait before diving or snorkelling this site.

Location: Ocean Grove, Victoria 3226

Abalone Dive Site
Abalone Dive Site
© Mark Norman, Museum Victoria

Divers have the opportunity to catch Abalone at this dive site. Remember your catch bag, legal abalone tool, current Victorian Recreational Fishing Licence, and abalone measure. Please abide by all current fishing regulations if you intend to catch abalone.

See article-catching-abalone for practical abalone hunting advice from The Scuba Doctor, plus melbourne-abalone-dives for a list of other Abalone dive sites near Melbourne.

Crayfish Dive Site
Crayfish Dive Site | © Ian Scholey

Divers have the opportunity to catch Southern Rock Lobster (aka Crayfish) at this dive site. Remember your catch bag, current Victorian Recreational Fishing Licence, rock lobster measure, and cray tags. Once you get back to the dive boat, or shore, make sure you clip the tail and tag your Crayfish as per Fisheries requirements. Please abide by all current fishing regulations if you intend to catch crays. See article-catching-crayfish for practical cray hunting advice from The Scuba Doctor, plus melbourne-cray-dives for a list of other crayfish dive sites near Melbourne. For tips on cooking your Crays, please see article-cooking-crayfish.

Wathaurong (Wadda-Warrung) country
Wathaurong (Wadda-Warrung) country

Traditional Owners — This dive site is in the traditional Country of the Wathaurong (Wadda-Warrung) people of the Kulin Nation. This truly ancient Country includes the coastline of Port Phillip, from the Werribee River in the north-east, the Bellarine Peninsula, and down to Cape Otway in the south-west. We wish to acknowledge the Wathaurong as Traditional Owners. We pay respect to their Ancestors and their Elders, past, present and emerging. We acknowledge Bunjil the Creator Spirit of this beautiful land, who travels as an eagle, and Waarn, who protects the waterways and travels as a crow, and thank them for continuing to watch over this Country today and beyond.

 

The Ledges Location Map

Latitude: 38° 17.346′ S   (38.2891° S / 38° 17′ 20.76″ S)
Longitude: 144° 34.378′ E   (144.572967° E / 144° 34′ 22.68″ E)

Datum: WGS84 | Google Map
Added: 2018-01-12 11:00:00 GMT, Last updated: 2022-04-29 12:55:18 GMT
Source: Allie Beckhurst GPS (verified)
Nearest Neighbour: 18 Metre Reef, 86 m, bearing 313°, NW
Ocean Grove, Barwon Coast.
Depth: 12 to 16 m.



DISCLAIMER: No claim is made by The Scuba Doctor as to the accuracy of the dive site coordinates listed here. Should anyone decide to use these GPS marks to locate and dive on a site, they do so entirely at their own risk. Always verify against other sources.

The marks come from numerous sources including commercial operators, independent dive clubs, reference works, and active divers. Some are known to be accurate, while others may not be. Some GPS marks may even have come from maps using the AGD66 datum, and thus may need be converted to the WGS84 datum. To distinguish between the possible accuracy of the dive site marks, we've tried to give each mark a source of GPS, Google Earth, or unknown.

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