It has a tubular, segmented body of an approximate length of 3.8 cm (1.5 in)[2] covered with chaetae, small appendages that aid the worm's mobility.

Each spiral is composed of feather-like tentacles called radioles, which are heavily ciliated and cause any prey trapped in them to be transported to the worm's mouth.

S. giganteus, like other members of its family, possesses a modified radiole, usually called the operculum, that it uses to secure its hole when withdrawn into its tube.

When they reproduce, they simply shed their gametes straight into the water where the eggs and spermatozoa become part of the zooplankton to be carried by the currents.

When the worm retreats into its tube, the opening is shut using an operculum, which is further protected by sharp, antler-shaped spines.

They use their brightly colored radioles to filter microorganisms from the water, which are then deposited straight into the worm's digestive tract.

The variously colored worm crowns make extremely popular underwater photographic subjects for sport divers.

Many aquarists who have miniature reef aquaria purposely include heads of coral that S. giganteus specimens inhabit.