Azolla rubra  

Aquatic, floating, dark-red (when exposed) or glaucous-green plants, forms ovate to ovoid patches on the surface of water bodies. Branching irregular; roots peg-like, simple: not branched. Leaves triangular; apex rounded; margins membranous, translucent; surface smooth, bright red or glaucous-green. Microsporangiate massulae spherical, surface conspicuously barbed. Megasporocarps brown, partially obscured by leaf lobe (NZPCN, 2013)

Common names include; Large mosquito fern, Red Water fern, Duckweed fern, Fairy moss