Abbey River Tideway where there are two larger islands. It is much smaller than Canvey Island and the Isle of Sheppey and narrowly ahead of Andersey Island facing Abingdon-on-Thames, another market town with an abbey which had multiple medieval mills, another of note being Westminster Abbey, the island of which Thorney Island no longer exists. The outfall of the Abbey River is 400 m above Chertsey Bridge, into the weir pool of Chertsey Weir. The manmade strictly-considered "island" the bypass channel forms is outranked in size since the 2002 completion of the Jubilee River by the example containing Dorney and Eton, Berkshire.
Tamar–Tavy Estuary Seaweeds, green algae and communities of polychaete worms are all found in the estuary system; near Calstock is found the shrimp "Palaemon longirostris", which has been recorded in only two other estuaries in Britain. The estuary is also one of only two sites in the UK where the fish, allis shad, spawn. Other larger animals found in undisturbed parts of the SSSI include the European otter, the common kingfisher and dormice. Tamar–Tavy Estuary The Tamar–Tavy Estuary is a Site of Special Scientific Interest (SSSI) covering the tidal estuaries of the River Tamar and the River Tavy on the border between