Sunbathers head to the public beaches along the shores of Alta Lake. Wayside Park, at the south end of the lake, has a beach, a canoe launch, an offshore pontoon, a grassy area with picnic tables, and hiking/biking trails. At Lakeside Park, also on Alta Lake, Whistler Outdoor Experience (604/932-3389, www.whistleroutdoor.com [1]) rents canoes for $24 an hour or $72 per half day, and kayaks for $20 an hour.
For a little white-water excitement, try river rafting with Whistler River Adventures (604/932-3532 or 888/932-3532, www.whistlerriver.com [2]), which provides guided scenic and white-water tours between the end of May and early September. Outings range from an easier float down the Green River for $69 per person to the white-water thrills of a full-day trip on the Elaho and Squamish Rivers for $159.
Links:
[1] http://www.whistleroutdoor.com
[2] http://www.whistlerriver.com