Tomboy and the swimsuits. yes one of those days.?

Hello people. I'm someone who is a tomboy and i simply can't stop being a tomboy because I am not use to wearing something other than t shirts and pants. so i have an issue with swimsuits because to me I am usually uncomfortable with the bikinis because parents disapprove. So to get right to the point. I like to wear boarddshorts with something like this as a top http://store.nike.com/us/en_us/?cp=USNS_KW_0611081618&l=shop,home#l=shop,pdp,ctr-inline/cid-1/pid-376843/pgid-298102 and uh lol i'm 13. and will the shirt flip up when diving? if it does.. i guess it's okay if ita like this http://store.nike.com/us/en_us/?cp=USNS_KW_0611081618&l=shop,home#l=shop,pdp,ctr-inline/cid-1/pid-376707. Thanks if you can help mme find something similar of those two because I really want to go swimming, but i don't know what to wear since I'm not use to wearing all those stuff. LOL SO thank you.