Yep, cause your lungs are full of air when you're floating & stationary. Once you start moving and breathing, your upper body and head are too heavy for your underwater buoyancy to support!
( . . . believe me, I know! Been there, sunk in bodies of water all over the continental U.S. and Caribbean!)
48 posted on 09/27/2006 4:29:19 PM PDT by AnAmericanMother
((Ministrix of Ye Chase, TTGC Ladies' Auxiliary (recess appointment)))