The four sides of a boat are the bow (front), stern (rear), port (left side as you face the bow) and starboard (right side as you face the bow). "Amidships" is used to refer to the center of the boat.
Similar terms often used aboard a ship include "aft" (towards the ship's stern), "fore" (toward the bow), "leeward" (the side opposite the direction of the wind) and "windward" (the side from which the wind is blowing). Others include "athwartship" (on either side of the boat), "aloft" (above the ship in the mast or rigging area) and "belowdecks" (on a lower deck or somewhere beneath the main deck of the boat).
