It's called the hull (pronounced hul). It's the lowermost part of a ship - the part of the ship that is submerged under water. The "line" along the center of the bottom of the hull of the ship is the keel of the ship. It's laid down first when the ship is built, and is a structural component. It could be looked at as the "backbone" of the ship.
The very bottom of a ship is where you find the keel. The keel runs the full length of the ship along its centerline and is the backbone of the hull. From the keel all the frames run out and up. the hull is attached to the frames. Picture the keel as the backbone and the frames as the ribs. The hull is the watertight skin that allows the ship to float. Within the hull are compartments (rooms) and at the top of the hull is the main deck. The superstructure is built upon the main deck.
The bottom of a car
curved keel
It's called the hull (pronounced hul). It's the lowermost part of a ship - the part of the ship that is submerged under water. The "line" along the center of the bottom of the hull of the ship is the keel of the ship. It's laid down first when the ship is built, and is a structural component. It could be looked at as the "backbone" of the ship.
The line at the lower part of the hull is the water line. Its location shows if a ship is riding high in the water or if it can't be seen then a ship is riding low in the water.
The front part of a ship is called the stem. It is connected to the keelson and keel.
line segment
The main body of a ship is called the hull. The hull runs from the main deck of the vessel all the way to the keel, which is at the center of the vessel where both sides of the hull join under the water. The part of the ship that is built above the hull is called the superstructure.
The hull of a boat is the body of the boat. it is the part of the boat in the water. excluding the mast, boom, sail, rudder, keel, etc.
The waterline is an imaginary line witch a ship or boat floats. The warmer or colder the water the less or more it floats. WIKI --- Waterline
It's called a line segment.