The Humber Forts are two large fortifications in the mouth of the Humber estuary in northern England: Haile Sand Fort (53°32′4″N 0°2′1″E / 53.53444°N 0.03361°E / 53.53444; 0.03361 (Haile Sand Fort)) and Bull Sand Fort (53°33′43″N 0°4′3″E / 53.56194°N 0.0675°E / 53.56194; 0.0675 (Bull Sand Fort)).
They were built in 1914 to protect the entrance to the estuary. They stand 18 metres (59 ft) above the water and have a diameter of 25 metres (82 ft). There was accommodation for 200 soldiers. They took three years to build and construction finished at almost the same time as the war. During World War II they remained as a deterrent and were regularly attacked by enemy aircraft. During this time a netting was put up to prevent enemy submarines travelling up the estuary to Hull or Grimsby.
Haile Sand Fort is around the low water mark between Cleethorpes and Humberston on the Lincolnshire coast.
Bull Sand Fort is 1.5 miles (2.4 km) from shore off Spurn Head. It is a 4 storey masonry building with 12-inch (300 mm) armour, with 4.6-inch (120 mm) guns, built with great difficulty as its sandbank is 11 feet (3.4 m) below low water. There are plans to convert it into a drug detoxification centre.