Done it in Dominica, good sturdy walking shoes with good grip are a good idea I think. Rucksack for the gear, leaves your hands free to hold on to stuff!!
I thought about a backpack, but this is the only time I will use it during the whole week and I have to think about space in my suitcase as I am flying to the embarkation port. But then again, I was thinking about bringing my own snorkel gear, so maybe this will work.