At very low tides it is possible to view the remains of an ancient mixed forest on the beaches of Mablethorpe and Sutton on Sea. It was submerged by rising sea levels about 3000 years ago. The first scholar to publish an analysis of this submarine forest – and of any submarine forest – was the Portuguese botanist and polymath, José Francisco Correia da Serra, who surveyed it in 1796, when he visited the area in the company of the distinguished naturalist Sir Joseph Banks. Sea flooding was a periodic problem during the Middle Ages. The last flood was the North Sea flood of January 1953, when a ten-foot storm surge broke through the flood defences.