Despite its name, Swamp Lake is a lovely little destination in the William O. Douglas wilderness near Mount Rainier. It's popular with fishermen and backpackers, though it can be extremely buggy in early summer.
Beginning at the Swamp Lake Trailhead, set out on a relatively flat trail. Within half a mile, you'll need to cross the Bumping River, which can be dangerous during high water events, like spring melt or after a rainstorm.
About three-quarters of a mile from the trailhead, cross into the William O. Douglas wilderness and begin climbing slightly. Hike through second-growth forest towards a creek crossing, then the trail levels out a bit, before climbing a bit more. Cross the outlet stream of Swamp Lake at 3.5 miles from the trailhead.
If you're camping here for the night, please remember to pitch your tent 100 feet back from the lakeshore. Swamp Lake is in a restoration area and the marshy land around the lakeshore provides habitat to animals living in the area.
While Swamp Lake is an excellent destination, the Swamp Lake Trail continues on, crossing the American Ridge Trail after climbing up a hillside for about 0.8 miles. At this intersection, hikers can turn left to visit Cougar Lake, or keep right to head for American Lake and, past that, an intersection with the Pacific Crest Trail.
WTA Pro Tip: It is possible to make this a longer overnight by starting your approach from the Bumping Lake trailhead. This allows you to walk along the Bumping Lake shoreline. This adds 3.85 miles one-way, but allows hikers to skip the ford of Bumping River.