Oh Be Joyful Creek

If you're not already camping there, park at Oh Be Joyful Campground, about 5 miles up County Road 734 from downtown Crested Butte. There's parking on either side of the river crossing, but you're going to have to get your feet wet anyway, so might as well park in the first parking lot and walk across the creek. 

To get to Oh Be Joyful Creek, you'll want to walk through the campground and start going up the hill to the west (see artist's renditioning of the journey in the pictures). You'll see a creek down below. The water level might be too high earlier in the summer, but in late summer and early fall, you should be able to wade up the creek if you want. Just be careful, as it can be a bit slippery in places. If you prefer, there's a trail along the right side of the creek that will still get you to the waterfalls. 

Essentially, once you get to the creek, just explore up it as far as you want. There are 4 or 5 small- to medium-sized waterfalls in the first half mile or so and you'll likely find a perfect swimming hole all to yourself. Just remember to pack out any trash you have and leave this spot pristine for the next visitor!