Sea snail

Live sea snail, species Nataea, photographed in situ

A species of sea snail in its natural habitat: two individuals of the wentletrap
Sea snail is a common term for gastropods which live in the sea (marine gastropods). It is not a formal term, just a term in common use.

Charonia, the shell of a sea snail called Triton's trumpet
Sea Snail Media
The shell of Syrinx aruanus can be up to 91 cm long.
A 50-second video of snails (most likely Natica chemnitzi and Cerithium stercusmuscaram) feeding on the sea floor in the Gulf of California, Puerto Peñasco, Mexico.
A hermit crab occupying a shell of Acanthina punctulata has been disturbed, and has retracted into the shell, using its claws to bar the entrance in the same way the snail used its operculum.