The Green Shark is a fish cryptid reported from Northumberland, England.
On September 16, 1757, a 6 foot "green shark" was caught in a net in the River Tweed near Berwick Bridge in Northumberland, England.
A man named John Sykes recorded the event, saying "As soon as it came near the shore, it made the water fly to a prodigious height, and after they had disabled it a little, and got it into shoal water, it made a hole in the sand with its tail which would have held a coach". When the captured shark was processed, a knife was found in its belly.
Some gentlemen thought that the shark, which had been in the East Indies, had tracked the East India Fleet to English waters and had followed the salmon up the river.
Bull sharks are well known for being river going sharks, but they are not distributed in this area. On the other hand, blue sharks, which are also distributed around the United Kingdom, were recorded to have traveled 1.5 km up a river in Shizuoka Prefecture, Japan, in 1976 or 1977. It is highly possible that the "green shark" was a blue shark like the one in the Shizuoka case.
Blue shark caught in a river in Shizuoka Prefecture.