River Thames shipping coming in and out of London, in 1732 it received the world's first lightship. This became a major landmark, and was used as an assembly point for shipping. Today it is marked by Sea Reach No. 1 Buoy. The River Thames contains over 80 islands ranging from the large estuarial marshlands of the Isle of Sheppey and Canvey Island to small tree-covered islets like Rose Isle in Oxfordshire and Headpile Eyot in Berkshire. They are found all the way from the Isle of Sheppey in Kent to Fiddler's Island in Oxfordshire. Some of the largest inland islands, for example
Columbia River Estuary Columbia River Estuary The Columbia River Estuary is an estuary and a bay on the Oregon–Washington border and the Pacific Coast of the United States. If the Columbia River Estuary is defined by the region that experiences ocean tides, then the estuary extends up the Columbia River to Bonneville Dam and up the Willamette River to Willamette Falls (south of Portland at Oregon City, Oregon). If the estuary is defined by the geographic land form or by the inland extent of salinity, then the estuary extends only as far as Welch Island. The downstream end of the estuary is the