Do you really want a 14 year old experimenting with cold medication while he is on vacation? Do you want a 14 year old reading the above links that you and I have provided to make a decision on what medications to take so that he can dive?
I don't. Which is why my response was simple.
OP, please skip the meds, enjoy snorkeling and other activities that others have suggested. You have so many years ahead of you for amazing diving experiences. When you get to be my age (old), you will have thousands of dives under your belt. I envy you a bit to be honest.
Kosta