A gelatinous, non-calcified bryozoan that is yellow or pale brown in colour. Colonies are stalked and stand erect from the substrate. The colony grows in finger-like lobed branches, and frequently exceeds 30 cm in height. When undisturbed, small white lophophores emerge from the surface. A. diaphanum is widely distributed and abundant in the coastal waters of the British Isles and the southern North Sea. Colonies are often dragged up in fishing nets, especially in the "weedy" areas of Dogger Bank, where this bryozoan is particularly abundant.