Taylor Swift kicked off her Independence Day celebrations one day early -- and with American royalty, to boot!
The "Both of Us" singer, 22, was photographed sailing with recent high school graduate Patrick Schwarzenegger, 18, and his extended family around the Kennedy compound in Hyannis Port, Massachusetts, July 3; Swift was also joined by her BFF, Glee star Dianna Agron, 26.
Swift, Agron and the Kennedys -- including Robert Jr., Ethel, Ted, Rory and Patrick -- continued to enjoy the weather on shore. Once night fell, "they were all playing capture the flag and tag and had a bonfire," an onlooker tells Us Weekly. (Patrick's mother, Maria Shriver, is the daughter of politician Sargent Shriver and his wife, Eunice Kennedy Shriver.)
"Taylor was taking photos of everyone with a huge camera and Dianna took one of Taylor with Patrick together," the onlooker adds. "She mostly hung out with her girlfriends and played with the smaller kids."
Schwarzenegger -- who will begin his freshman year at the University of Southern California this fall -- tweeted that the holiday was "the best 4th of July I could ask for. Hope everyone had a great day!"