Officers were called to the scene at 11.39am on March 29 to reports of a man in the water.
Police said the man is in his 20s.
The incident is not being treated a suspicious, the police said.
Passers by have been taking to Twitter amid the emergency service presence.
At around 2pm today (March 29) crowds are expected to come together on Westminster Bridge to remember the victims of the terror attack one week ago today in which four victims lost their lives .
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