As the mercury rises, look for more refreshing ways to workout, without sacrificing the intensity. Singer Mariah Carey dives into her swimming pool workouts, rain or shine, to do 45-minute water aerobics classes four to five times a week, according to Shape magazine. These pool exercises helped her shed a whopping 70 pounds since giving birth to her twins Monroe and Moroccanlast year. "Swimming is my favorite form of exercise, which is surprising since I almost drowned in the ocean when I was 6," says Carey, who mimics running, biking and weight lifting in the water for maximum results with minimal risk of injury. Enroll in a water aerobics classes near you or even head to the beach with a friend on your next vacation to get your pre-baby body back.