Need to delay period?

This month, on the 26th, I am leaving to go on a cruise... I am 16 my period is irregulear becaue I just started in October. Im supposed to get in like on the 22nd, and lately my period has been coming really close to the day it is supposed to come. I cannot have my period on my cruise because we r swimming with sting rays and stuff, and I cannot where tampons no matter how hard I try. I did some resear ch and found Norethisterone. I dont know much about it. Do you have any inf (how it works, where to get it, how old,). My mom will agree I think but im not sure, So Ijust want info about it. The only doctor I have is our family doctor.