If you want to build an armada for the sea employ these ships to ram
in the enemy's ships. That is, make ships 100 feet long and 8 feet
wide, but arranged so that the left hand rowers may have their oars
to the right side of the ship, and the right hand ones to the left
side, as is shown at M, so that the leverage of the oars may be
longer. And the said ship may be one foot and a half thick, that is
made with cross beams within and without, with planks in contrary
directions. And this ship must have attached to it, a foot below the
water, an iron-shod spike of about the weight and size of an anvil;
and this, by force of oars may, after it has given the first blow,
be drawn back, and driven forward again with fury give a second
blow, and then a third, and so many as to destroy the other ship.

The use of swimming belts.