The caab is found in some medieval encyclopedias, particularly that of Thomas of Cantimpré. It is said to be a marine animal with small feet relative to its large body, with feet like those of a cow. It has one long boneless foot (or leg) that it uses as a hand to bring food to its mouth.

The "caab" as a marine monster is the result of a misinterpretation by Thomas of Cantimpré of the text from Aristotle, as translated from Arabic to Latin by Michael Scot (1220 CE). Thomas thought the word cahab referred to a marine animal. It is actually a transliteration of an Arabic word for "ankle" in Aristotle's description of the elephant. This misunderstanding led to Thomas's creation of the caab, a fish with many of the attributes of the elephant [Sedinova, page 65-66].