Unfortunately, this is just one of those things women have to deal with. You can't delay your period on purpose. However, it could be late again next month on its own if your cycle is changing a bit (common for young women your age) or the change of routine in the trip and stress of going can cause you to be late. I use tampons in the pool, no problems. So, think about that to take along for ease of water sports and period. good luck