Cruises, Windstar Cruises. The harbour was dredged in 2016 in preparation of the arrival of and , the Navy's first supercarriers, with regular maintenance dredging taking place at various times of the year. Site of Special Scientific Interest Most of the harbour is composed of intertidal mudflats and cordgrass marshes, and they have abundant benthic fauna which provide food for birds. It is of national importance for dark-bellied Brent geese and for three species of waders, grey plover, black-tailed godwit and dunlin. Proposed Tunnel A tunnel crossing the mouth of the Harbour between Gosport and Portsmouth was proposed in 1941, which would have allowed pedestrian traffic while doubling as a subterranean air raid shelter for residents on both sides. This proposal came during the Blitz, which saw Portsmouth and Gosport bombed heavily. The proposal, termed the "Kearney Tube" after the Australian engineer conducting the initial study, evolved into a proposal for rail link tunnel in 1942, but the project was never constructed. In 1999, a study was undertaken by the Light Rail Transit Association in regard to a proposed tunnel crossing to alleviate traffic congestion in the area, particularly Gosport. Of three construction methods examined, an immersed tube was deemed to be the most effective, as it would not necessitate closing the harbour for over a year, but rather a series of shorter closures of around 24 hours for the addition of each segment of the tunnel. The tunnel would be approximately 1 km in length, though only around 670m of this would be underwater. The tunnel would have been part of a light rail network connecting Fareham, Gosport and Portsmouth. The South Hampshire Rapid Transit Order 2001 provided authorisation for the project, with construction intended for 2002, but financial problems delayed this. The Department for Transport ultimately declined to fund the initiative in 2005. See also Portsmouth Harbour railway station References Further reading External links Current nautical charts of Portsmouth Harbour and approach channel Live streaming web cam overlooking Portsmouth Harbour Gosport Portsmouth Transport in Portsmouth Geography of Hampshire Ramsar sites in England Sites of Special Scientific Interest in Hampshire Competent harbour authorities Tourist attractions in Portsmouth Ports and harbours of Hampshire Special Protection Areas in England