Fourth of July weekend is well underway, and several stars have already slipped into swimsuits for some holiday fun. Kourtney Kardashian kicked off the festivities [1] by hitting up Miami Beach with a few pals, while Alessandra Ambrosio escaped to Ibiza [2] with her fiancé, Jamie Mazur, and their kids, Anja Louise and Noah Phoenix. Lea Michele [3] enjoyed a relaxing day at the pool, and Reese Witherspoon [4] put on her pink snorkeling gear and went swimming under the sea. And that's just the beginning! Read on to see how the rest of Hollywood is celebrating, and then take a look at the Obamas' patriotic Independence Day celebrations over the years [5].