Question about swimming with your period?

Ok so i got my period on monday, and today is wednesday. Im going camping on friday and going swimming in a pool at the campground, so the water isnt dark. Do you think my period will stop by friday? And also if it doesnt, how can i go swimming? Does it stop when in the water, and if it does how quick should i change? I dont want to use a tampon either...so please help!