The Ceacilian (not to be confused with "Sicilian") is an amphibian. Sometimes also called "Rubber Eel" or "worm" they are neither eels nor worms. They are not really fish either yet are offered in pet stores for aquariums, for fish tanks.
Rubber is the natural, elastic product that is obtained from the secretion of a certain plant. The term rubber is also applied to the materials that synthesized from petroleum derivative-chemical like styrene and butadiene.