[1] Fontinalis is characterized by its dark green color, and irregularly branching stems covered with small to large glossy, sharply ridged leaves.

Aquatic adaptations of sporophyte-associated features in Fontinalis include: perigonia with few antheridia (1, 2, or 4–6); enlarged, well-developed vaginula; immersed or emergent, very thick-walled capsules; lack of stomata; and peristomes with endostomial trellises.

[4] Fontinalis occurs primarily in clean, acidic freshwater across Afro-Eurasia, Iceland, and the Americas, attached to submerged rocks and logs.

The family of nematoceran flies, Chironomidae, is known to use these moss as a habitat, alongside other insects such as Pteronarcys, Hydropsychidae, Rhyacophila, Ephemerella, Leuctra, Nemouridae, and even Simulium in areas where the water is sufficiently fast.

[1][2] Fontinalis is also particularly sensitive to heavy metals, with water coming from copper pipes known to damage the genus over extended exposure.

Young Fontinalis mosses emerge between late winter and early spring, going through intense growth spurts in the mid-summer.

However, growth slows in late summer, and in autumn these mosses adopt an unhealthy appearance, turning olive green, then brown, then black during the winter.