Fishermen on the shore caught a four-foot-tall humanoid, with duck-like feet and a tail protruding from its back. It tried to escape but was killed when the fishermen beat it with sticks (like humans apparently do whenever they encounter something weird). Another fish-man was caught a few months later in the same area, though this one was described with more seal-like qualities. There are actually a surprisingly large amount of merbeing sightings that were reported in 1737 - and so maybe they were following some kind of a migratory pattern?
Source: 'Humanoid Encounters' by Albert Rosales
Image Credit: http://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectId=3370709&partId=1&subject=16589&page=2
