[marigold]

Okay, you got me curious now. Would the bubbles need to be methane, or would ordinary air bubbles work as well? Assuming there is no explosion involved.

Carting a load of air around underwater sounds safer and more environmentally-friendly than a load of methane.

[steamroller]

This sounds suspiciously like high school physics-not a strong subject for me.I will now have a "test coming up/didn't study" nightmare (LOL)

[MHGinTN]

Any gass will do. We have means by which solids can be mixed to produce huge free quantities of gases, but in war, forget the environmentally freindly crap ... war is inherently environmentally dangerous.