Bo - who sports a white chest, white paws and a white goatee - was named by the Obama daughters.
He was a gift from a close friend of the family, Democratic Senator Edward Kennedy of Massachusetts.
Mr Kennedy, who owns three water dogs himself, said in January that he was "proud to endorse the Portuguese water dog as the next First Dog of the United States".
He said the breed would be a "perfect fit for the Obama Family" as the dogs have a "can-do and hopeful spirit" and were smart, resilient, determined, optimistic and tireless.
The choice of the US presidential pooch had been a pet topic for the nation's press ever since Mr Obama promised his daughters a puppy during the campaign.
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