Nacre (mother of pearl) is that crystalline substance that lines the inside of shells. The mollusk secretes an organic substance, Conchiolin, that lines the inside of the shell protecting it from parasites. It is an iridescent layering that shimmers colour as light bounces off the surface. The sandbars and reefs that are contained in the shallow basin in front of the Roper and Limmen Rivers are a thriving ecosystem that remains undiscovered. Because of the remoteness of the area marine research and a scientific database is lacking. Perhaps there is a currently unknown mollusk endemic to the area.