Grab some hydrogen peroxide from the pharmacy
Chuck in it a catalyst like
bleach or
catalase (chopped up livers will have enough of that enzyme) or
any metal oxide, it think manganese dioxide is the classic
..............and it will release oxygen.
Just do that and breathe close to that sh!t and you will be in an O2 rich environment dude
Or easier, get a plumber friend. .......he will have an oxy-acetylene set, turn on the pipe and suck awa,,,,,,,,, The black cylinder, not the red one.
But anyway, good luck with the
singing underwater (which seems to be more of a technical issue than the
duration of the underwater stint)
but you do know you can do a number of takes and put them all together, like in The Abyss the actors were not actually underwater for 120mins

