Are you rowing out to the dive site in your boat made from coconut wood, wearing a wetsuit made from woven reeds? Not me. I admit to being a big polluter. On my trip before last, someone even complained about me pissing in the sea.
Well maybe that someone was wondering why you need to expose yourself on deck instead of using the head, which (depending on location) is treated/blended etc.
this is totally OT but I gotta agree with JB on this, the only way we are gonna leave no footprints is to NOT go there...no sunscreen even? oil from the boats that we use ? it s all over the dive site bro...
ok coming back to your point about leaving the stains on your casing, hey I say..go for it !
Doesn't it make more sense to reduce pollution whenever possible? What's wrong with using biodegradable sunblock, or to stay on topic, using vinegar to clean the housing at the end of the trip? If the argument since there is no way to completely remove pollution, let's just keep on polluting without worrying about it, then we would not have 4 stroke, much lower polluting engines which replaced the 2 stroke pollution. Etc etc.
Anyhow, ascetic (white vinegar) or citric acid(lime/lemon juice) should remove all the water marks, and you don't need to do it too often. If you must have a new looking housing after every dive, then wipe down your housing with such a solution after every dive and keep it out of the sun by covering it.