In order to ground the boats, the bottom of the hull had to be flat and, as a matter of fact, the centre body of the vessels under consideration is wide and flat, wider even than that of the vessels from the North. The beam of these latter was to the length as 1 : 4, while in most of the Mediterranean vessels this proportion varies between 1 : 2½ and 1 : 3½ (generally, 1 : 3).
The Mediterranean boats are pointed toward the stem and the sternpost, which is the contrary of what exists for the Northern vessels and this shape gives the former an appearance all their own. Furthermore, the sides of these ships do not come at all together toward the top; at most, they are vertical; in other words: the greatest width is at the top.
Among the old models, some are found which have: 1º a straight sloping stem; 2º a straight vertical stem, and 3º a curved stem which is convex or concave at the top.
Alongside of the broad-beamed vessels, there are a few longer ones, of which the beam is to the length as 1 to 5.
Intentionally, no mention has been made of the sternpost as this has been modified in most cases by the adoption of the rudder.
Besides, many boats have a flat projection at the stern furnished with a balustrade,—a detail which is found also on the Greek and Roman vessels. This position was originally reserved for the helmsmen who operated the steering oars.
Among the more important types must be counted the Xebecs, with three masts furnished at the beginning with lateen sails. These latter were replaced later on by square sails. The ship thus modified was then called a mystic Xebec or a polacca Xebec. The Polacca also existed at this time.