Walk It Off Research shows that people who walk four hours a week--that's just over 30 minutes a day--weigh nearly 20 pounds less in midlife than those who don't exercise regularly. Related research shows regular walkers are half as likely to develop heart disease--one of the leading killers in our sport. You don't even have to do all your walking at once to get benefits. Three 10-minute walks a day will help you shed fat and strengthen your heart. Warm Up Most of us wouldn't step onto the golf course, tee up and start driving away without taking a few easy swings to get the blood flowing. It's equally wise not to jump into the water without warming up. A good warm-up boosts circulation and lubricates your joints and muscles so you can shimmy into your wetsuit, hoist your tanks, and get up and down the ladder with ease. And it's easy to do. Perform a couple of simple squats. Do push-ups against a wall. Put your hands on your hips, and twist your torso left and right. Make easy windmills with your arms. Pay attention to places in your body that feel tight and give them a stretch. That's it. With just two minutes of easy activity, your muscles and joints are ready for the rigors ahead. Make Some Muscle It's not your imagination--that 50-pound tank really is getting heavier! Sometime after we blow out the candles on our 30th birthday cake, we start losing up to a half-pound of lean muscle tissue a year. That means less strength and, because muscle fuels your calorie-burning metabolism, more fat. Turn the tide with a little strength training. U.S. Navy research shows you can replace two pounds (nearly five years' worth!) of lean muscle tissue and shed four pounds of fat by doing just four strength training exercises three times a week. Do these core four moves (three sets of 10 repetitions) starting today: Simple squat: Stand, holding dumbbells at your sides. Squat down like you're sitting in a chair until your thighs are nearly parallel to the floor (don't let your knees jut past your toes). Return to start. Chest press: Lie on your back holding dumbbells over your chest with arms extended. Lower the weights until your upper arms are even with your chest. Press back to the start. Bent-over row: Stand, holding dumbbells. Bend forward from your hips until your back is nearly parallel to the floor, with your arms hanging down, palms back. Pull the dumbbells to your chest, then lower. Criss-cross crunch: Lie on your back, knees bent 90 degrees and legs lifted so calves are parallel to the floor. Place your hands behind your head. Lift your right shoulder off the floor and curl toward your left knee as you extend your right leg. Switch sides. Drink up ... Dehydration increases your risk for DCS. Hydration experts recommend drinking half your body weight in ounces, especially on the days leading up to a dive. All liquids count (well, except booze), but water works best. ... But Not Too Much Speaking of fluids (or "unfluids"), mounting evidence shows that a beer (or other adult beverage) or two a day is good for your heart, but more than that is a buzzkill for your body, especially if you plan on diving. Alcohol is well known for its dehydrating effects. But more importantly, booze messes with your anterior cingulate cortex--the error detection center of your brain. That's really bad business before a dive. Having too much also can hurt you the day after. Hangover doesn't just lead to headache, fatigue and poor brain function; studies show it also stresses the heart and increases your risk for cardiac death. Flex Your Feet Unless you're a ballerina, the only time you spend an hour or so pointing your toes and flexing your feet is when you're 50 feet down, finning like a fish. The result can be painful foot cramps. The best way to avoid them short of dancing in silk slippers: "Toe grabs," says Martz. "This simple move can strengthen the muscles that support your arch, so they're less likely to fatigue and cramp up on your next dive." Do it twice a week. Sock pickup: With bare feet, grab a sock with the toes of your right foot and, keeping the heel planted, lift it off the floor. Hold for one second. Release and repeat until your foot fatigues. Repeat with the left foot. Strengthen Your Support System Weak back and ab muscles open the door to low back pain, especially for divers who spend so much time bowed like a U as their legs drift up behind them. Ab crunches can prevent some pain by strengthening the muscles that support your torso. But research shows the fullest protection comes from flipping over and working your spine supporters through their entire range of motion. Do crunches and extensions (described below) twice a week. Back extension: Lie facedown with your arms bent and hands folded underneath your forehead. Lift your head, shoulders and torso off the floor as is comfortably possible. Return to start. Repeat eight to 12 times. Breathe Deep Scientists have found that practicing yoga can help improve your lung function and breathing capacity. But you don't have to be a yogi to breathe better. Get similar benefits by stretching your chest muscles, which helps open the chest cavity, and practicing deep breathing to expand your active lung capacity. You can even do it right at your desk: Raise your arms out to your sides and pull them back as far as possible. Hold that position and take five or six deep, full breaths. Relax. Repeat daily.