Warnstorfia fluitans is a medium-sized moss ranging in color from green to yellowish to brownish and can be rarely red when the species occurs in exposed habitats.

Its alar regions are narrowly transversely triangular and roughly reach the costa.

However, these morphological features are inconsistent in W. pseudostraminea, and rarely certain occurrences of W. fluitans have the same characteristics.

It is often found in fens, bogs, depressions in rocks, on moist rocky surfaces, and other similar watery areas ranging in elevation from 0–3,500 m (0–11,483 ft).

The moss can be found throughout Canada and the northern United States, variously in South America, Australia, and Eurasia, in southern and eastern Africa, and on islands in the Atlantic, Pacific, and Indian oceans.