Islamic polities of the classical period recognized the importance of seaweeds in their daily life. Their men of science, craftsmen, and navigators used them for medicinal purposes, manufacturing, and navigation. The agar components were used in treating pathological conditions such jaundice, spleen, kidney and skin ailments, and malignancies. As food, we stress that our conclusions derive from Qur'ān-based commentaries and Muslim religious law that encouraged seafaring and exploiting the resources of the sea. Concerning navigation, sailors could identify coastal trunk routes, shallows, and various marine phenomena; shipwrights used agar compounds as a protective coating against the Greek Fire. Like their Greco-Roman counterparts, Muslim physicians, chemists, botanists, and professional sailors of this period were acquainted with numerous species of seaweeds and could appreciate the actual scientific importance of each type as well as the aquatic environment where these species lived and developed. Their scholarly literature consists of several generic Arabic and Arabicized terms to denote seaweeds and the terms variations appeared to be physical rather than linguistic.