It is commonly found attached to the stems of water plants, the undersides of leaves, submerged twigs and on the surface of stones.

Gently sweeping through a clean weedy pond and allowing the collected water and leaves to stand in a jar will often reveal Hydra emerging after only a few minutes.

When in feeding mode, the fully extended tentacles are very long and may exceed 1 inch (25 mm) in length.

The relative length of the tentacles compared to the body is characteristic of the species and serves to differentiate it from any other brown Hydra of cool temperate waters.

When a cold sensitive strain of H. oligactis is subjected to temperature stress, it undergoes a shift from asexual budding to sexual reproduction.