All three will only take a total of 15 minutes, but can really have an impact on how you look! They are easy to do and target exactly the muscles you want to hit if you want to get hit on at the beach.
1.) Purchase an exercise ball (found in any sporting goods store). Lie on your back on the ball and make yourself comfortable. Place your hands behind your head while keeping your back and neck straight. Don't pull on your head! Instead, contract your abdominal muscles so you are performing crunches on the ball. Do this for five minutes.
2.) Lie on the floor on your back, and then lift your legs up to as close to a 90-degree angle as you can. Once you've lifted your legs as high as you can, lower them very slowly to the ground. Repeat this process for five minutes. As you do this exercise more and more often, you should be able to lower your legs more and more slowly.
3.) Pick up a broom and then sit on a chair. Hold the broomstick across your back, making sure that your elbows are bent at a 90-degree angle. Make sure you are holding the broomstick with your hands and not your back or shoulders. Without moving your hips, rotate your upper body right and left as far as you can. Keep this up for about five minutes. As time goes on, you should be able to move your body back and forth further and further.