We snorkeled at several beaches but there wasn't much to see, especially compared with Maui which had better visibility and more underwater life; Tunnels Beach was the best of the ones we visited
I've visited the 9/11 Memorial a couple of times so skipped it on this trip; One World Trade Center (ie Freedom Tower) is still jaw-dropping as the tallest building in the Western Hemisphere (the same architect designed Willis Tower and Burj Khalifa)