Oriental Moon Snail

Found burrowing in soft sediment, over inter-tidal, to deeper, sandy areas of reefs. They produce a collar-shaped egg-mass.
They feed on bivalves.

These are predatory sea snails that envelope their prey and then bore a hole through the shell using its radula, injecting an acid secretion. Once the shell is bored open, the proboscis is used to consume the flesh of the prey.
In the breeding season, the female moon snail lays a rather stiff egg mass which includes sand and mucus. These objects wash up on sandy beaches fairly often, and are known by the common name "sand collars" because of their resemblance to an old-fashioned removable shirt collar or false-collar.