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)
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