I have to swim on my period?

So I'm only in highschool and this week we have a boat race for my physics class. It's in the pool and even if were not paddling the boat then we need to be in the water. And of course I just started my period so I have to use a tampon right? I usually wear pads but are tampons ok for water? Is there a possibility it will leak or something? I just need some advice!