After reading this thread it sounds like a rebreather might not be suitable for my diving after all - as a photographer the first aim of every dive should be to not damage the reef at all, and increasing my profile still further with a bailout tank while doing macro photography won't help that. When you are shore diving and carrying multiple housed dSLR's there is a practical limit as to how much you can walk in with and not end up falling on your arse, and I think that a bailout tank would put me over that limit. To be honest I hadn't really considered the need for a bailout tank as my diving isn't usually beyond about 20 metres, I was planning on using a BOV, but I hadn't realised that a BOV could be rendered useless by a caustic cocktail - damn!

So I guess it's a question of which one comes first - the rebreather that is caustic cocktail proof... or a quieter form of open circuit. One day there will be the perfect piece of kit.