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Segmented worms. The segmented worms are the most abundant and diverse of all the groups of reef worms. Divers are familiar with the feathery feeding parts of the tiny Christmas tree worms (Spirobranchus) which extend from lumps of living coral. The body of the worm is hidden in a tube within a Pontes coral head. The similar, but larger fanworm, or feather duster worm (Protula, Sabellastarte), secretes a tube of flexible parchment to protect its soft body. From its tube, it periodically extends a crown of colorful "feathers" to collect plankton. These worms make good subjects for macrophotography, but any sudden movement will cause them to withdraw their crowns.

The triton shell, Charonia tritonis. This gastropod preys on crown-of-thorns starfish.

The helmet conch, Casis cornuta. Indonesians call this kirn a kepala kambing, the "goat's head shell."

Some of the segmented worms have evolved unusual reproductive strategies, perhaps the most famous being that of the palola worms, (Palola siciliensis). Called nyale in parts of Indonesia, these worms spend their lives in coral crevices, but one night a year, their tail parts metamorphose into a sexual form, containing either eggs or sperm.