David Fleetham / Red encrusting sponge (Clathria sp) on calcium carbonate-producing Seaweed / Green algae (Halimeda kanaloana). Hawaii.

Franco Banfi / Sponge probably (Clathria (Axosuberites) nidificata) on rocky seabed. Antarctic Peninsula, Antarctica, Southern Ocean.

Shane Gross / Close up of Red velvet sponge (Clathria pennata). Browning Pass, British Columbia, Canada. North East Pacific Ocean. July.