Sand weed Rhodothamniella floridula
This seaweed consists of tiny horizontal filaments made of strings of cells, from which arise other filaments that reach a maximum height of 1 in (3 cm). The upright filaments have irregular side-branches, some of which interweave to form a complex network that traps sand grains. This network builds up to form a spongy mat about in (1 cm) thick. The mat sometimes covers large areas of rocks that are next to sand and creates a habitat for small animals such as nematodes.