sea fort
fortification at sea
Fort Sumter
fort in Charleston, South Carolina
Horse Sand Fort
sea fort in the Solent off Portsmouth, Hampshire, England, UK
Fort Heath
US seacoast military installation for defense
Bull Sand Fort
sea fort in Humber estuary, Easington, East Riding of Yorkshire, England, UK
Fort Jefferson
fortified island in Florida, USA
Pampus
island in Netherlands
Scola Tower
sea fort in Italy
Fort Carroll
historic fort in Maryland, USA
Humber Forts
two sea forts in the Humber Estuary in Northern England, UK
South Channel Fort
island in Victoria, Australia
Fort of Saint Nicholas
fortification in Rhodes, Greece
Fort Mahon
Fort located on the coast of the Strait of Dover, northern France
Fort Denison
heritage-listed former penal site and defensive facility in Sydney Harbour, Australia
No Man's Land Fort
Grade II listed sea fort in the Solent, UK
Nab Tower
lighthouse east of Isle of Wight, UK
St Helens Fort
sea fort with lighthouse in the Solent close to the Isle of Wight, England, UK
Fort Boyard
fort in Charente-Maritime, France
Fort Alexander I
Fort near Kronstadt
Pope's Eye
uncompleted foundation for an island fort at Port Philip, Victoria, Australia