If you take the tampon method, I would actually suggest that you don't go deep-sea snorkelling/diving lar. Near the beach SHOULD be fine. Sharks really are attracted to blood... would you want to die because of a leaky tampon?

The meds that delay your period are usually oral contraceptives, actually. While not quite as bad as some people may lead you to believe, they do cause quite a range of possible side effects even from short-term use. These would be inconsistent or irregular periods after stopping them, as well as mood swings, weight gain, acne etc.