I'm trying to figure out how deep a column of water I would need to stop a .22 bullet. I'm interested in recovering bullets from a series of guns and trying to see those 'characteristic striations' each gun leaves as part of its 'fingerprint.' For what it's worth, Mythbusters tried to address this but didn't use .22 caliber, only larger bullets. Oddly enough, if we extrapolate down in caliber, it would seem to me that the .22 will penetrate farther than the higher caliber bullets. I don't know anything about fluid dynamics, which might help me understand how a small projectile traveling through water would dissipate its energy. It would appear in this site that a 10-foot tank is used to obtain control bullets from test fires. http://www.firearmsid.com/A_BulletID.htm Thanks!