Try Rowing (250–600 calories)
Water is 775 times denser that air, so moving against water pressure while swimming strengthens and tones muscles from your fingers to your toes. But unless you're doing laps above your local coral reef, swimming rarely offers much in the way of visual stimulation. Not everyone lives near a lake, river or reservoir, but for those who do, rowing is a much more scenic way to work your quads, glutes, shoulders, abs and biceps on the water. Sculling with a friend or a team also dispels some of the loneliness of the long-distance swimmer. Many groups practice on the still, calm waters of the early morning, sometimes setting out before dawn, so there may be a local boathouse or club that you've just never noticed before. Check USRowing.org to find a club near you.