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Student with a set of twin 75 cu ft alloy tanks.



By Andrew Whitehead

Published in Dive Log Australasia
July 2001


Divers who enrol in the Deep Diver Specialty course at Absolute Scuba usually enrol in the Wreck Diver course around the same time. The skills go hand in hand for diving on the SS President Coolidge in Vanuatu and the Japanese wrecks in Truk Lagoon. I enjoyed those deep wreck dives because I undertook the appropriate training beforehand, and bought the new bits of gear that make it safe. Now it was my son’s turn to make that next big step: learning the skills to dive beyond the recreational limit of 30 metres, and to use the additional safety equipment that goes with it.


The five students on the May course completed their self-study requirements and arrived for the evening theory session at the shop in Capalaba, Brisbane. I sat in on the course as Neil Harris delivered his own PowerPoint presentation, complete with humorous anecdotes and good advice. After the theory, Neil presented the various bits of equipment that can or should be used in deep diving. Out came the twin tanks, pony bottles, sling tanks, hang tanks, high performance regulators, Tech BCDs, various manifolds, air-integrated computers, backup gauges, reels, lift bags, etc.

The Gear

As you can see, this is an equipment intensive course requiring careful dive planning and configuration of the appropriate gear. During the four dives that made up the practical part of the course, each student would practice the skills involved in using the additional safety equipment.

They would also have one dive using a set of twin 75 cu ft alloy tanks. Neil bolted each student’s BCD to the tank bands when it came to their turn. Two separate regulators were then attached with an air-integrated computer and backup gauges.

For the other three dives the students would use 12 litre working capacity (100 cu ft) steel tanks containing double-filtered air. On these dives, they would take turns in carrying pony bottles or sling tanks as part of the training exercises.

I went along as a pleasure diver equipped with big 15 litre (120 cu ft) steel tanks containing EAN 30, and a 3 litre pony bottle containing EAN 36 as a deco mix. The tanks all have high pressure DIN valves so they can be filled to their maximum working pressure of 230 Bar. The main tank and pony bottle have a combined working capacity of 18 litres, and provided me with a total of 4,140 litres (or 144 cu ft) of gas. Each tank had an oxygen-cleaned Nitrox regulator and gauges attached. In addition, I wore a Nitrox computer on my wrist pre-programmed with these gas mixes. A depth alarm at 37 metres limits the partial pressure of oxygen to a maximum of 1.4 Bar when using the main tank. The pony bottle, with its higher percentage of oxygen, would not be used below 29 metres. This is not technical diving, just safe recreational diving.

The Vessel

With eight divers on board and eighteen tanks, the big red 7.3 metre Zodiac Absolute Won tore across Moreton Bay at its cruising speed of 30 knots. Aboard were skipper Steve, instructor Neil, Mike, Karen, Ben and Robert, and three deep water pleasure divers: Bill, Robbie and me. There was a light southwest wind which left the Amity Point bar virtually flat, and gave us a smooth ride out to Point Lookout on North Stradbroke Island.

Moreton Bay was supposedly named by Captain Cook, however history books say that he was actually looking at the ‘bay’ formed by the northern shore of Stradbroke Island and the east coast of Moreton Island, and he spelt it differently! From his low observation point on the Endeavour, he had no way of knowing that there was a major river flowing into a large bay behind what he thought was the coastline. Anyway, our Moreton Bay is protected by the surrounding islands which are made of ancient sand, except for some rocky formations which form a line of reefs and the two headlands, Cape Moreton and Point Lookout.

Middle Reef

We anchored over Middle Reef which is roughly half-way between Flat Rock and Shag Rock, north of Point Lookout. This is a rocky reef with sand at 27 metres, ideal for deep diver training. We had a look around in a few gullies, then the students deployed two lift bags from reels and practiced an open water ascent using these devices. Since Neil and I were both using Nitrox, we had a little more bottom time than the divers on air. I signalled that I was within three minutes of deco so we headed back to the anchor line and made a slow ascent with deep stops at 20 and 10 metres, and the usual 3 minutes at 5 metres.

Boat Rock

With such great conditions, we headed east to Boat Rock which is well out from North Stradbroke Island. This small, isolated rock is not often dived because it is usually rough with strong currents sweeping past. I was pleased to go there because this would be only my third dive there, but I consider it to be the top dive site in the Point Lookout area. It is suitable for advanced divers because the rock drops steeply to a depth of thirty metres. We anchored on the sheltered northwest corner in about ten metres of beautiful blue water. There was a large turtle in the distance as we descended the anchor line, but it was too far away to identify. The visibility was superb at about 25 metres. Neil took us over a sheer drop to the bottom at 27 metres past two large Wobbegongs which were asleep under a ledge. The students went through their various exercises with the secondary air supplies while I poked around the rocks looking for interesting marine life.

We returned to Boat Rock for our first dive the following day and were able to anchor fairly close to the rock. While the students were practicing their skills at 32 metres, we three pleasure divers swam along the eastern side of the rock where there is a wide ledge like a narrow road, at about 20 metres. Robbie and Bill explored a deep cave underneath the ledge while I watched a group of eagle rays cruise past. I switched to my pony bottle during the ascent to take advantage of the 36 percent oxygen mix which reduced my nitrogen loading.

Flat Rock

After an early lunch of chicken, salad, soft drink and Mars Bars, we found some more superb conditions near the big bommie at Flat Rock. We anchored in 33 metres over “Dave’s Drop-off” where it was Robert’s turn to use the twin tanks. Rob bolted his BCD to the bands and attached his own regulator and AIR II to the right hand tank. A set of Cyklon regulators on the left tank had to be clipped in a secure but accessible position.

During the dive, we found a big turtle asleep at the end of a gully with his head and half his shell in a cave. Bill was rewarded with a few minutes of deco time for going down to have a closer look. We explored under the big boulders that form the wall on the outside of the bommie, then crossed to the anchor line for a nice slow ascent.

The students all demonstrated a high level of competence in their deep diver skills and also had a great time doing it. They were subsequently awarded with their Deep Diver certificates.

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