The gastropods, more commonly known as snails and slugs are among the few groups of animals to have become successful in all three major habitats: the ocean, fresh water, and land.
Gastropods are characterized by the possession of a single (often coiled) shell into which the animal can generally withdraw, although this is lost in some slug groups.
Slugs are snails whose shells have been reduced to an internal fragment, shed after their larval stage (Nudibranchs) or completely lost in the course of evolution.
There are over 3,000 recorded Nudibranch species, and these are noted for their often extraordinary colours and striking forms. Nudibranchs are often seen at many of the dive sites around Koh Lanta.
Some gastropods are scavengers, feeding on dead plant or animal matter; others are predators; some are herbivores, feeding on algae or plant material.