Michele has it right, based on my reading of the info about on-line booking. If you want to make a change, you need to re-enter your whole list of excursions. The last on-line request you do is the one that "counts."

By the way: if you reserve a PG scuba dive on-line, you still need to go the the dive desk when you get aboard. They'll need to see your certification card and, depending on your answers to the standard PADI forms they use, might need to see your doctor's letter indicating you're OK to dive.

george