A staple of elite swimmers and water-polo players, the wall-walk push-up will build your chest, upper back, and shoulders. It will also test your balance, which bolsters the abs. To begin, prioritize form over number of reps—the move requires coordination, so a few practice tries are necessary. And be warned: It will hurt more than you think it will. Start with three sets of six to eight reps, resting a minute between sets. As it becomes easier, gradually increase the reps and decrease rest time, and do it every other day. Put the effort in now—you'll have plenty of time to chill when your newly sculpted torso hits the sand.
Start in push-up position, your hands just inside the plane of your shoulders. Walk your feet up the wall, about a foot above the floor. Your body should form a rigid plank parallel to the ground. Squeeze your core throughout the move. With your feet still on the wall, do a single push-up, slowly lowering your chest to the floor and pressing back up.
Next, keeping your spine and neck straight, walk your hands back toward the wall while stepping your feet up the wall until you're in a handstand position.
Keeping your toes on the wall, hold the handstand for a beat. Walk your hands back from the wall while stepping your feet back down the wall, returning to the start position. That's one. Immediately start the next push-up.