Portsbridge Creek (also Port Creek, Ports Creek and Canal Creek) is a tidal waterway that runs between Portsea Island and the mainland from Langstone Harbour to Tipner Lake. Through its history it has been made navigable a number of times and it is today navigable for small boats.
The creek and in particular the creek's crossing has been the site of defensive works possibly as far back as the reign of Henry VIII of England.
During the English Civil War Royalist forces attempted to hold the parliamentarian forces at the creek during the early stages of the Siege of Portsmouth. Defences consisted of a wooden barricade mounted on the bridge backed by a small fort equipped with 4 guns. The guns were withdrawn on 10 August 1642 and with the barricade held by as few as 8 men the parliamentarian forces were able to cross the creek two days later.
A fort at the site of the crossing of the creek turns up in plans from 1660 and 1666. The fort was rebuilt in 1688 under the direction of the Chief Royal Engineer Sir Martin Beckman.
It has been suggested that the presence of a customs officer in Cosham was to deal with attempts at landing contraband from Portsbridge Creek.
The waterway was made navigable by the Portsmouth & Arundel Navigation company in 1830 after the failure of the Portsea Canal. The work to deepen the creek cost £1000. It proved difficult to keep the creek clear for navigation and a canal called the Cosham Canal to provide an alternative route was proposed, although it was never built. The canal company abandoned the creek in 1838. An army report on the status of the Hilsea Lines made in 1853 mentioned that the creek was filled with weeds to the point where for 3 to 4 hours every day it could be walked across. Later in the decade as part of upgrade works on the Hilsea Lines, the creek was widened and deepened to allow it to be used by gunboats. Dams and flood gates were constructed at the ends of the creek to allow it to be kept it in water at all stages of the tide. The remains of one of these dams can be seen at the eastern end of the creek.