The Hull.
This is the main part of the ship. It is divided into three sections, namely the fore part, the midships part and the after part. The fore part ends in the stem, which is the leading edge of the hull. The after part ends in the stern, which is the rear end of the hull. The midships part is the section in the middle of the hull. When one is standing anywhere inside the hull he is facing forward if he faces the stem. When he is facing aft he is facing the stern.

Any line which runs lengthways in a ship is said to run fore and aft and the line joining the stem with the middle of the stern is called the fore-and-aft centre line.

The vertical plane running through the fore-and-aft line divides the ship into two halves. When facing the stem, the starboard side is on your right hand and the port side on your left.

The vertical sides of the hull meet at the bottom of the hull at the keel, which is the backbone or spine of the ship. The curved (vertical) surface at the fore part of the ship is called the bow. The equivalent (sometimes curved) surface at the after part of the ship is called the quarter. The centre part of the ship is referred to as amidships.

When a ship is afloat, the waterline divides the sides into the ship’s side above the waterline and the bottom below it. The continuous horizontal surfaces of a ship are called decks. If their surfaces are exposed to the elements, they are called weather decks. Those that are not continuous are called flats or platforms.

Terms applying to the hull.
The following nautical terms apply to the hull of a ship:

Freeboard. The height of the highest continuous deck (upper deck) above the waterline at any point along the hull.
Draught. The depth of the keel below the waterline at any point along the hull.
Beam. The greatest width of the hull.
Camber. The curve given to the surface of decks so that the water will drain away to the sides.
Bilge. The nearly flat part of the bottom of the hull both inside and outside the ship.
Bilge keel. A long projecting fin welded onto the sides of the ship’s bottom to decrease the rolling of a ship. It is normally welded to the hull at the turn of the bilge.
Sheer. The upward sweep of the upper deck from amidships towards the forward and after ends.
Tumble home. When the ship’s side curves or slopes inward above the waterline they are said to tumble home.
Flare. When the ship’s side curves outwards above the waterline they are said to be flared.
Flush deck. When the uppermost deck in a ship is continuous from stem to stern, unbroken by any raised or sunken portion (except upper works or superstructure).
Transom. The older ships used to have a curved stern which was referred to as a cruiser stern. Most modern ships have a flat ended stern and this is called a transom.

The forward section of the upper deck is referred to as the forecastle (foc’sle).
The after part of the upper deck is referred to as the poop(deck). On SA and RN warships it is referred to as the quarterdeck. The decks on a warship are numbered consecutively downward with the forecastle or upper deck being 1, the next down being 2 and so on. The decks above the forecastle/upper deck (ie in the superstructure) are numbered consecutively upward with a zero preceding it, ie 01, 02, 03 etc.

The structure built above the upper deck is called the superstructure. It consists of a number of decks housing, the accommodation or living quarters, offices, electronic equipment rooms, store rooms and the bridge. On a warship it houses certain officers’ quarters, the bridge, operations centre and weapon control facilities.
The bridge is usually situated on the highest deck of the superstructure since it is from here that the ship is navigated and controlled.

Typical bridge.

The chartroom is usually situated just aft of the bridge or on the bridge itself. This is where the navigator/officers of the watch navigate the ship from, where the navigation equipment is kept and the control and display units of the navigation systems are mounted
The wheelhouse or steering position of a modern ship is found in the bridge. On older warships it was situated just below the bridge.
An operations centre is found on a warship. It is situated below the bridge in the superstructure. This is where a warship is controlled from during hostilities.

Typical layout of a general cargo vessel (Admiralty manual of seamanship).

A merchant ship has holds where they store cargo. They are below the upper deck and are numbered consecutively from forward to aft.
The decks below the upper deck are referred to as ‘tween decks’. The lowest part of the hold is referred to as the lower hold.
A flat is a platform which does not run the length or breadth of the ship, ie the tiller flat (the compartment situated right aft where the steering motors are mounted).