Did ancient Mediterranean shipbuilders at the turn of the first millennium have methods to pre-design the shape of their hulls prior to the construction of the ship? If so, can these methods be identified? This paper proposes that ancient shipwrights were in possession of such design methods, based on geometry, that are comparable to the medieval and post medieval hull-design procedures called whole-moulding. These methods are well suited to be transformed into rules-of-thumb, therefore allowing the storage and transmission of accumulated knowledge. The implications of this proposal on the present understanding of the transition from shell- to skeleton-building are explored.