Snails belong to Gastropoda . They have a single, coiled shell. A pair of sensory tentacles come off their head with eyes at the end. Their mouth has a rasping tongue, called the radula, to shred food. Parasitic worms may live in them.
Snails move by a muscular, slimy foot under their body.
Algae naturally grows on most aquatic snails. It provides some camouflage. Information on pond snails is sorely lacking on the internet and in books. I have not included any information on land snails as I know very little. Reproduction Most snails are hermaphrodites.