Sightings of sea serpents have been reported for hundreds of years, and continue to be claimed today. Cryptozoologist Bruce Champagne identified more than 1,200 purported sea serpent sightings. It is currently believed that the sightings can be best explained as known animals such as lungfish, oarfish, whales, or sharks (in particular, the frilled shark). Some cryptozoologists have suggested that sea serpents are relict plesiosaurs, mosasaurs or other Mesozoic marine reptiles, an idea often associated with lake monsters such as the Loch Ness Monster.
Reported sea serpent sightings on the coast of New England have been documented from 1638 onwards. An incident in August 1817 led a committee of the Linnaean Society of New England to give a deformed terrestrial snake the name Scoliophis atlanticus, believing it was the juvenile form of a sea serpent that had recently been reported in Gloucester Harbor. Sworn statements made before a local Justice of the Peace and first published in 1818 were never recanted. After the Linnaean Society’s misidentification was discovered, it was frequently cited by debunkers as evidence that the creature did not exist. (Wikipedia)