My "breather" finally got out for a dive this month. After a couple of false starts earlier in the month, I packed the scrubber, checked the battery voltages, lubricated the o-rings and reassembled the Inspo (Australian slang for the Inspiration rebreather) ready for a freshwater dive in Lake Taupo on Sunday 10th April.
During the positive pressure test after assembly, there was a loss of pressure in the rebreathers loop. With the aid of soapy water, the leaks were quickly found and resolved (a small leak in the exhale hose connection to the counterlung tee-piece and from the dump valve.) The unit now held both its positive and negative tests. The auto diluent valve (ADV), manual inflators and Auto Air all worked without any problems.
Nigel Lees drove Dave Maddox and myself across to Lake Taupo via the Forgotten World Highway. After almost three hours of snaking through tight turns and unsealed sections of road and we were standing at the side of the lake in a small settlement called Pukawa. Our three Inspirations were unloaded quickly from the vehicle and the side slung tanks (for open circuit bailout off the rebreather loop) were placed at the waters edge for putting on in the water. After calibrating the rebreathers to account for altitude (Lake Taupo being at a height of 356m above sea level) and ambient air pressure, we pulled on our drysuits, strapped on the VR3 dive computers, and donned the Inspirations for pre-breathing the scrubber.
Pre-breathing the InspoAs always, a small group of onlookers watched as we approached the water and proceeded to ask the usual set of questions. Nigel took the role of spokesman for the day and answered with a knowing tone which seemed to appease the onlookers curiosity. I was getting too hot in the drysuit and walking about with the 32kg rebreather didn’t help, so I made a beeline for the water and geared up. Nigel and Dave pulled on their fins and side-slung tanks in the water. Dave had a 40cu.ft. aluminium tank, Nigel was using a 7litre Faber steel tank and I had a 10litre Faber steel tank (with an extra connector allowing it to be used as an off-board diluent source via the ADV.)
We all submerged and met up at the edge of a ledge in 3m of water. Here we checked for any bubbles (a sign of a leak in the unit) and adjusted the gear for comfort. Dave set off down the steep slope with Nigel and myself following behind. The water was 18C and the visibility dropped to about 8m after 18m of descent. Setpoints now at 1.3bar and using a modified frog-kick, we pushed out deeper following the now gently sloping contour of the lakes’ banks to a depth of 38m (Lake Taupo can get to a depth of 160m in places and we were diving a spot that went to 85-90m.) A thermocline in the water at 27m made the temperature drop to 15C and it was very noticeable (I heard Dave let out a yelp as he passed through it!)
Nigel was photographing the cheeky freshwater lobsters. At only 3-4 inches long, they would try and take you on by jumping up and snapping their pincers at you. The lake bottom is composed of mud with a fine silt sitting on top. Great care with buoyancy and finning technique are required to prevent a silt out. After 35 minutes of bottom time we turned and followed the slope upwards, taking care to stop at our first required stop depth.
The steep slope had occasional large rocks embedded in it. These rocks seemed to be places where small fish and freshwater lobsters congregated (they looked like they were having committee meetings or something very similar.) Nigel and Dave pressed their masks up close to one such gathering, but nothing seemed overly bothered by their presence. Ah, the joys of no bubble diving!
It was time to play at 14m with Dave deploying a DSMB (Delayed Surface Marker Buoy) which was yellow and had the word "EMERGENCY" written down its length. This type of SMB is fired off when there is a problem on a dive and assistance is required! When he pulled it out and was about to inflate it, I grabbed his attention and asked if he really wanted use that particular SMB and not his orange one for doing deco on. Dave signalled back that all was well and the SMB shot off to the surface dragging the line out of his reel effortlessly.
With all our stops completed, we switched our setpoints to 0.7bar just before the 3m ledge and made our way up the shore. In water shallow enough to stand in we closed our mouthpieces and walked out of the water. Very quickly we were all reminded of how heavy the units are when not supported by the water.
A quick check on the dive computers showed a runtime of 77 minutes.
We got all the gear packed and loaded into Nigel’s vehicle and then we headed home with one stop for refreshments and a blueberry muffin.
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