it happened to me before

i was so scared getting into water as i couldn't really swim. ha. we went out as a group at a resort, i kept drinking seawater, then i cried saying nos, then they explained to me again (well, probably it was lost in translation) i then realized that i wasn't doing it right. u need to bite on the mouth pieces and suck on the tube, and relax, some self talk will help haha...
never panick even if u see a shark..