Makes me think of the guys in the rock quarry a few years back testing the homemade sub...
Made out of a propane tank of all things!

They had an ad in the local newspaper looking for volunteer 'Safety' divers for the testing of the sub...

Somehow, 'Safety Diver' and 'Volunteer' is a phrase I didn't think was a really good idea!

Anyway, it worked OK to about 100 feet, the depth of the quarry while we were there...
Don't know how it turned out from there!