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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.

Shearwater Research Petrel 2 - RUN OUT SALE

Shearwater Research Petrel 2 - RUN OUT SALE

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Suunto EON Steel Black Wrist Dive Computer

Suunto EON Steel Black Wrist Dive Computer

$1,499.00
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Mandeville Road, Summerlands

Reef Dive Reef Dive | Boat access Boat access

Advanced Open Water Rated Phillip Island Reef Dive Site

Depth: 2 m (6.56 ft) to 12 m (39 ft)

Manderville Road, Summerlands is an impressive dive when visibility is good. The site lies to the west of one of Australia's most popular tourist destinations, as every evening hundreds of tourists are bused out to see the sunset penguin parade nearby.

The site features include large basalt reefs and canyons and bommies offshore along the cliffs. There are a series of large, dramitic bommies between deep chasms and gullies about 200 metres offshore. The area is very exposed to southerly swells.

Location: Summerlands, Phillip Island, Victoria 3922
MELWAY Ref: Page 731 B7

Getting To Manderville Road, Summerlands: You can get there by taking Ventor Road (C473) and turn right onto Manderville Road, heading south until it intersects with The Boulevard. The latter is a dry weather road that runs from the end of the Nobbies Centre parking lot and marked as an alternative route to the penguin parade. It hugs southern Summerland Peninsula, a jagged shoreline with dramatic points and inlets resembling a geological sawblade. The longer drive is worth it just to take in the amazing views. It goes all of the way around to join with Ventor Road near the Phillip Island Penguin Centre. Starting out from the Nobbies Centre parking lot you can drive along The Boulevard until it intersects with Manderville Road. The Boulevard is one-way from the Nobbies Centre to Mandeville Road, and two-way from the penguin parade to Mandeville Road.

Boat Dive Only: Ian Lewis in "Shore Dives of Victoria" descibes this as a shore dive. However, while you can still get above the dive site via Manderville Road or The Boulevard, you're not permitted to park or walk off track. All areas off track on Summerland Peninsula is defined as a prohibited area. There are no access tracks down from The Boulevard to the south coast by foot or other means. Also, there is no suitable parking in these areas and parking your car off road is also an offence under the regulations of Phillip Island Nature Parks. This is all in the name of protecting habitat for penguins and other wildlife that nest right up to the roads. People walking through the penguin colony run the very real risk collapsing burrows and accidentally killing birds. So this dive site is only accessible by boat.

Entry/Exit: This is a high energy open sea zone prone to all of the vagaries of changing Bass Strait conditions. A high level of experience and caution is required.

Ideal Conditions: The best conditions at Manderville Road, Summerlands come after several days of still weather and offshore northerly winds. Enter at high tide, whenever it is safe to do so. See WillyWeather (Phelands Bluff) as a guide for the tide times and the height of the tide.

See also, Summerland: Mandeville Road in "Shore Dives of Victoria" by Ian Lewis, 3rd edition page 152.

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.

Boon Wurrung / Bunurong country
Boon Wurrung / Bunurong country

Traditional Owners — This dive site is in the traditional Country of the Boon Wurrung / Bunurong people of the Kulin Nation. This truly ancient Country includes parts of Port Phillip, from the Werribee River in the north-west, down to Wilson's Promontory in the south-east, including the Mornington Peninsula, French Island and Phillip Island, plus Western Port. We wish to acknowledge the Boon Wurrung 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.

 

Mandeville Road, Summerlands Location Map

Latitude: 38° 30.958′ S   (38.515971° S / 38° 30′ 57.5″ S)
Longitude: 145° 8.247′ E   (145.137456° E / 145° 8′ 14.84″ E)

Datum: WGS84 | Google Map
Added: 2022-03-11 21:36:25 GMT, Last updated: 2022-03-16 11:38:49 GMT
Source: Google Earth
Nearest Neighbour: Phelan Bluff, 1,076 m, bearing 83°, E
Phillip Island.
Depth: 2 to 12 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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