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Tritons. The triton shell (Charonia tritonis) is famous as a predator of the troublesome crown-of-thorns starfish, which has devastated Australian reefs. This large shell (to more than 30 cm.) is a popular souvenir, and over-harvesting has been blamed for population explosions of the crown-of-thorns. The helmet conch (Casis cornuta) is another large, predatory gastropod found in Indonesia. Because of collectors, both the triton and helmet conch are endangered in parts of Indonesia.

Cone shells. Cone shells (Conus spp.) are even more rapacious predators. Their radulas are modified as barbs, with which they stab their victims. They then immobilize their prey by injecting a neurotoxic poison. Most cone shells eat worms, although a few are piscivorous. The poison of some of the fish-eating Conus species is powerful enough to kill a human, so treat them with respect.

A predatory gastropod prying open a bivalve.

Cowries. Cowries (Cypraea spp.) are common, small (most just a few cm.) gastropods with a smooth shell that is completely covered by the animal's fleshy mantle. Both the shells and mantles can be beautifully marked, often with very different patterns. The cowries are omnivorous, feeding on algae as well as a variety of sedentary animals such as soft corals.