White Swimsuit on Period ?

So i got this reaaaally cute white swimsuit yesterday, without thinking that i’m most likely gonna be on my period when we go on vacation. I told my stepmom and she says that i’ll be fine as long as i put a tampon in, not to worry, etc. I read somewhere that you don’t really bleed as much when you’re in the water because of the pressure or something. Im just wondering the chances of actually bleeding through it? Or any advice for swimming on my period ?

*i know that i need to wear a tampon. i’m wondering the chances of bleeding through the tampon, and it getting on my swimsuit