Shawn Foust never intended to get hooked on skydiving. It all started with an unusual present from his wife for his 32nd birthday: the chance to plunge from a plane flying at 15,000 feet. On a clear day last November, the Seaside couple took a leap of faith together and they both signed up for training at Adventure Center Skydiving in Hollister. Foust, a federal agent with the Department of Defense, and his wife, an Air Force captain at Monterey's Naval Postgraduate School, had never embarked on anything like this, even during their military training.