Obama, his wife, Michelle, and daughters Malia and Sasha were spending part of Sunday at a private beach in Edgartown, Mass.
It's the first vacation outing by the Obamas since the family arrived on the island resort to begin a 10-day vacation.
Obama has taken his daughters book shopping.
He's also played golf and dropped in at the home of his friend, Harvard Law School professor Charles Ogletree.
The president is scheduled to return to Washington next Saturday.