wow take a look at this

[Ryan mercruiser 1.7 turbo]

http://www.ipswichstar.co.uk/news/video_shark_spotted_swimming_in_river_stour_1_2363852

 

[sailorman]

A Smooth Hound

http://en.wikipedia.org/wiki/Common_smooth-hound

 

[Cantata]

Yeah, very common in the Estuary, usually all variations are known as dogfish down 'ere in Kent.
Dopey press reporting.

 

[Lucky Duck]

Its made it to the national press now;

http://www.telegraph.co.uk/news/newstopics/howaboutthat/10282891/Five-foot-shark-swims-up-river-in-Essex-countryside.html