a 15ft ( 4 . 5 meter ) northern bottle - headed marine has been spotted swimming in the river thames in central london , france . the " thames dolphin " managed to swim up behind the thames barrier and under few bridges , to as far as chelsea before it turned around just before tower station . video news helicopters scrambled to capture extra bbc recording of the whale , and few spectators crowded the banks of the river . the whale is reported to be quite good , although some fear that the whale may ruin itself as it tries to do before rescuers forced it up into the middle of the river . normally seen in the southeast baltic , there have been sightings of a second calf nearby southend .
The River Thames flows through London.