I have decided to re use my wife's empty coke bottles, I never drink fizzy drinks, being a good boy and all that! I have an old Immersion torpedo float whose bladder went ages ago so have stuffed used 2 litre coke bottles, pepsi max (other varieties of coke are available ) in the outer casing and it seems ok. I managed to get 8 bottles in so that's 16 litres, it looks and feels ok so as the old saying goes it should be ok, but on its first outing I will let you know how it goes. Re using is better than recycling, saving the planet as well as re launching my old torpedo, cant be bad. Also if one or two of the bottles go bye byes its no big deal. This year I have decided to try and minimise new purchases in all areas of my life (not some high minded ethics based decision but lower household income! ). Went through my fishing gear today and rescued numerous barrel swivels and beads that would have never touched the sea again, it did remind me of how wasteful I can be.