Shiprock 21-05-11

Third dive for the day after the Tug and The split. I was using the remainder of my twins 27% Nitrox and my pony for back up. We dropped in tight on high tide and joined the other divers who had trekked down the steep track. Viz was normal for Shiprock - the air in the bubble cave was very stale so I took only 2 breaths from it before descending again. Along the wall we found an octopus who quickly receded into his hole. A large wobbiegong was resting in a small recess down from the bubble cave, I don't think any of the other divers saw it. I felt a bit out of place with twins and pony alongside all the rest on their singles but given their evident lack of experience I drifted while they rushed around all arms and legs. I switched from the twins to pony when there was 12 bar left - wanted to keep a bit for wing inflation. Only during our safety stop did I realise my computer was still set on 27% and I was breathing 21%! Given the nitrogen load from the previous dive this was not very smart and a a DCI risk. Thankfully I did not suffer any adverse affect.