We snapped the growing crowd of mingling celebrities and high society at the Mercedes Benz Polo Challenge, which got off to a slightly shaky start on Saturday. Although Debra Messing and Reggie Jackson did a perfect job ushering in the match, Debra almost didn't make it. On her way to Bridgehampton, she spent some tense time in the car trapped in heavy beach traffic. Luckily, Debra got there just in time and rolled the ball to mark the start of the fourth chukker. Guests in attendance included Michelle Rodriguez, Katie Lee Joel, Samantha Cole, and Denise Vasi, who all dressed in true Hamptons style for the event. More pics after the jump