to all of you darwin award candidates...
yes you can dive using this stuff, and perhaps it will be uneventful for you...but is it really worth dying to save a $100 hull cleaning bill...when you have no clue what you are fixing to do or how to do it?
As to the "spare air" containers...you better learn a bit about them...before you COUNT on them to save your life...you may get 10 breaths out of one, if you are trained, capable and don't panic
Scraping bottoms...are you going to enjoy eating (unless you have a full face mask, or hazmat) now broken barnacles, pollution and such...and are you going to find a decent wet suit or dry suit that will not shred when you "brush" against the barnacles and you will...or sure just slap some weights on...without regard to buoyancy or what happens if you have strapped on too much and can't get off the bottom while you regulator is "just a few feet" away..
get certified at least before you tempt these fates...and then you can tell which internet comments are clueless...and can get you hurt
and yes I am PADI AOW certified