Time to learn to put a tampon in. Get the kind that has a cardboard applicator, like Tampax. Get the box that has a variety of sizes, and start practicing with the smallest one. If you can feel it when it is in, you need to push it in further.
dear...i wil suggest not to swim...because during these days...body temperature increases...so keep your body in normal relax state....if you dont care then when you turn 30+ you will get certain joints and muscles problems....
I definitely would suggest learning to put in a tampon. I find things like Playtex Sport have the easiest applicator. You can swim just fine.
Without a tampon or something to absorb the blood, you run the risk of all sorts of embarrassment.
If you worried about toxic shock from tampons, try menstrual cups