>> tie up the legs tight just to make sure we don't waste air space by tying them too far up the pant leg. >> it's a skill that actually takes practice. by filling the legs with air, i've turned my pants into a life preserver. as for avoiding sharks, as experts told us last year in the bahamas, don't thrash around. you look like food. if you're with another person, link arms back to back to fight them off with your legs. you don't see land, what do you do? >> you just have to stay calm. and you can conserve your energy. >> dan says your number one enemy is panic. >> if i didn't have a float like a set of pants, another option would be our dead man's float. we fill our lungs with air. >> uh-huh. >> put yourself face down. and just let yourself float till you feel like you need to take another breath. >> a plunge from the air i won't soon forget. >> whoo. >> all to help you survive the unthinkable. matt gutman, abc news.