I moved your post to Caribbean Port Chat since it was not related to Carnival. We have been to Aruba and Curacao a few times. On both islands excursions from the ship took us to sunken ships. The water was crystal clear and there was plenty of sea life, no coral, but fish and turtles. The last trip to Aruba we went to Palm Beach, not sure if it is the same as Palm Island Beach. The beach was very clean, snorkeling was not great, but the water was very clear. The had a nice pier with a bar/restaurant. We went by cab from the port. Bonaire has better snorkeling as far as coral goes, but both Aruba and Curacao have great water and plenty of fish and turtles.
Hope you have a wonderful cruise!