Rafting is a popular activity for people who don't mind bumping around a lot and getting wet in the process! It's a good way to built group cohesion. And remember, there is no "I" in TEAM!
There are several outfitters in Fort Collins who organize Rafting excursions up the Poudre River canyon.
Follow SR 14 up the Poudre River canyon to find excellent places to launch your innertube. It's only about 20 miles north and west of the center of Fort Collins. Anset Watrous State Park, and the Roosevelt National Forest abut the Poudre as it cascades down the Rockies.