Serious sailors are not likely to live full time at this altitude; even weekend sailors would be wise to look elsewhere for their kind of fun. But if you insist on trying, you'll find a few sails spread on the bigger lakes of these mountains. You can take a pretty big boat on pretty big Flathead Lake, Jackson Lake, or even Yellowstone Lake if you're careful about the weather. Smaller boats such as Hobie Cats, in some ways, better suit the sudden, swirling winds typical of these mountains.
Powerboating is another matter; if you've got a motor, pack a lunch and head for any of the many lakes that dot Montana and Wyoming's landscape. Canyon Ferry is a popular Montana water-skiing spot, and you'll see Wyoming powerboats cruising Boysen Reservoir or the many impoundments on the North Platte. Just make sure to check around locally regarding access if you're uncertain about it. All types of boats are available locally for rent.
Canoeing, Kayaking & Rafting -- Paddlers have a wealth of choices here. Montana is particularly rich in rivers worth floating: the Flathead, the Blackfoot, the Madison, the Clarks Fork near Missoula, the Dearborn, the Yellowstone, and even the big old Missouri. In Wyoming there is less variety, but you'll find some fine stretches of river on the Snake, the Platte, the Hoback, and Clarks Fork through Sunlight Basin. If you choose white-water rafting, leave the driving to someone else (that is, sign up with an outfitter that will provide an experienced person to pilot your craft), though you may be asked to paddle. The smaller rivers have no dams to regulate flows, which means kayakers seeking fast, scary runs should come during runoff in June, while canoeists wanting to relax and bird-watch can easily handle the upper Snake or Flathead late in the summer. For thrills, try the Yellowstone River at Gardiner, Montana, and the Snake River in Wyoming.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.