Boooo! The ghostly apparitions at the Thames Estuary in Kent look like a spooky H.G. Wells scenario. They’re actually abandoned AA platforms on stilts, built in 1942 as anti-aircraft positions. Called Fort Maunsell, the guns fired at German bombers crossing the Channel to attack London and other English targets. For info about sightseeing cruises in the area, go to www.greta1892.co.uk