The Gullet is the stretch of water in the crownlands between Dragonstone and Driftmark to the north and Massey's Hook to the south. Blackwater Bay opens into the Gullet, which connects with the narrow sea.
During the Dance of the Dragons, the Gullet was blockaded by the fleet of the Sea Snake, Lord Corlys Velaryon. The greens tried to break the blacks' naval superiority with the Battle in the Gullet, to no avail.
A Clash of Kings