Boat trip to Green Island near Cairns is well worth it! The ferry picks you up and drops you off at the Island which takes about 20 minutes. You then have the choice of snorkeling or taking a glass bottom boat to see the reef. I took the glass bottom boat (being a not so confident swimmer!) and it was better than I expected! Saw many different types of fish and then walked around the island itself - lovely beaches and the clearest ocean water. Would definitely recommend for all ages.