Is it possible to make you period early by one day?

My period is supposed to start next week on Wednesday. That week im at a summer camp and we are going white water rafting on Wednesday. Its not really i have an issue with being on my period while im there because its usually not that bad for me, but if im going to be getting wet, im gonna need a tampon. But if my period hasn't started by that morning, then i cant put in a tampon because your not supposed to wear then unless you are actually on your period. But if my period starts while im on the river, there's not way to stop to go to the bathroom. And im not even sure if its going to start on Wednesday because ive only had my period for a couple months and its not exactly regular (usually off by a couple of days and im sure i did the math right). I am like so confused right now! My mom's away on a business trip right now and she keeps her phone off most of the time, and there's no way im asking my dad or brother about this lol! Please help me! Is there a way to start my period like just a day earlier so i can use a tampon, or how can i solve this problem without affecting my period?