Diaphanous Lake

Drainage: Stillwater
Approaches: Approximately 32 miles round trip from the Box Canyon trailhead, all on trail. FWP puts it at 16 miles from West Fork Stillwater or 15.5 from Upsidedown, both entirely on trail.
Elevation: 9,611 feet
Fish: Arctic grayling, stocked. Montana FWP.
Coordinates: 45.28416, -110.08671
Bugs: Mosquitoes, just bad enough to be annoying.

Getting there

FWP's line is that several trails from the Lake Plateau serve this lake, which is unusually easy company for this country. It is on trail from any direction.

We came from a camp at Wounded Man on the way to Mirror, about nine tenths of a mile north and 224 feet up, half an hour out.

The hike

Diaphanous is 8.7 acres and 25 feet at the deepest.

The fish story here is worth knowing before you carry a rod up. Rainbows were stocked in 1980 and appear to have died out. Five days of netting in 2003 for a whirling disease study produced nothing. FWP netted it again in 2018 and again found no fish.

Then in 2022 they put 850 arctic grayling in it, and their 2025 survey pulled 19 averaging 11 inches and running to 12.4. So the lake went from empty to a working grayling fishery in three years, and another 850 are due in 2028.

When we walked past, it was still the empty version.

FWP calls the camping excellent, though the firewood is somewhat picked over.

Tips & safety

• Navigation: On trail. Several routes off the plateau reach it.

• Camping: Excellent, with firewood somewhat picked over.

• Fishing: Grayling since 2022, running around 11 inches. Anything you read from before then describes a lake with nothing in it.

• Bugs: Mosquitoes, annoying rather than bad.