The International (403/859-2362, www.watertoncruise.com [1], early May–early Oct., C$32 adult, C$16 teen, C$10 child) has cruised 500-foot-deep glacier-dug Upper Waterton Lake since the Prince of Wales Hotel opened in 1927. The two-hour round-trip boat ride from the Waterton marina to Goat Haunt, Montana, at the southern end of the lake departs several times daily.
From the boat you’ll get good views of tower cliffs, waterfalls, and one mountain after another. From Memorial Day through Labor Day, hikers can hop off at Goat Haunt (provided they have the ID required to cross the international border), explore the trails there, and take a later boat back to Waterton.
For a short boat ride to a good hiking area, ride the water shuttle to Crypt Landing (403/859-2362, www.watertoncruise.com [1], mid-May–early Oct., C$16 adult, C$8 child 4–12) and hike 5.4 miles past waterfalls, up a short ladder, and through a tunnel to pop out at Crypt Lake [2], then catch an afternoon boat back to Waterton.
Links:
[1] http://www.watertoncruise.com
[2] http://www.moon.com/destinations/montana/glacier-national-park/waterton-lakes-national-park/recreation/hiking