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Dive Report: 02/04/97

PS Koputai - Off Bondi Beach


Deep rebreather dive and deep nitrox OC dive! 20 mins at 79m on Nitrox 26 Divers: Scott Leimroth, Rod Nairne(Homebuilt CC Rebreather) , Dave Apperly, Suzie Dudas.

The above photo shows Rod Nairne on the P.S. Koputai. You can see the remains of one of the paddle wheels in the background. Photo taken by the author while breathing nitrox 26.

The dive was to 78msw for 20mins. Dave Apperly, Suzie Dudas and me (Scott Leimroth) accompanied Rod on the dive using OC scuba and trimix for bottom gas. The weather was sunny, the water calm and there was no current. I descended first and upon reaching the bottom found the anchor to be on sand with the wreck not visible. I felt very narked even though my END for the dive was supposed to be only 50m. I also felt a forboding sense of impending doom, something wasn't right and my whole body was tingling, the same feeling you get when your arm goes to sleep if you sleep on it. I changed to my air reg and ascended to about 60m where I began to feel better and met Rod and Suzie coming down the line. I signalled that the wreck was not there, Suzie ascended while I stayed at 60m while Rod descended to the bottom. After a few minutes waiting for him I saw what appeared to be the OK signal coming from below - a torch moving in a circular motion. I assumed Rod had found the wreck so I switched back to bottom mix and descended. Upon reaching the bottom I found Rods torch tied to the anchor chain making the OK sign as it bobbed around the chain with the rope movement. In the distance I could see a strobe going off and realised Rod was on the wreck.

I swam the 20 - 30m to the wreck and found Rod who was taking photos. At this stage I still felt extremely narked but OK otherwise. I modelled for him on the engine and boiler and took the camera to get a few shots of him on the breather. By this time Dave had joined us and was exploring the wreck. After 20mins we headed back to the torch in the distance and began our ascent.

I mentioned how I had felt on the dive to the others once we were back in the boat and we all thought it was strange. Upon returning to the shop I topped of the remaining gas in my tank (about 50bar)with air and tested it to see what I had. To my surprise the PO2 was over 21%. After trying to figure how this could be, we realised with disbelief that I had taken the wrong tank and had actually been breathing 26% nitrox for the whole dive!!! This explained my strange feelings on the first descent, I had been in the early stages of CNS.


The above photo shows the author on the P.S. Koputai breathing 26% Nitrox at 79m.

How it happened - I'm an idiot!!

Before the dive Dave had accidentally let some of his nitrox deco mix bleed back into the air banks while he was filling and when I had filled my tank with air it had become nitrox 26. I left this tank at the shop and took another tank of air. Unfortunately both my tanks are black and I had mistakenly left my trimix tank and taken the 26% instead.

Oh well, I survived the dive, learnt some big lessons (clearly mark your tanks and be fastidious when filling and checking mixes) and had a full tank of heliair to take home for another dive. I was instantly nicknamed "Tingles" by all those present.


The above photo shows the author decoing on Nitrox 50 after surviving a 20min dive to 79m using Nitrox 26 as a bottom gas. You work out the PO2, CNS and OTU's

Ask the A.A.R.G.