How are airplanes, ships, submarines and automobiles electrically grounded?

Both Ships& Submarines are large steel (usually) hulled object in direct contact with the earth(Seawater is a very good conductor). 

The distribution system on ships is usually a Insulated Neutral system which prioritizes continuous machinery operation over safety of humans. In case of 440V 3-phase , supply is not bonded to hull(વહાણનું ખોખું). Advantage of this system is that ,if one of the phases becomes grounded it won't cause a fault & distrupt the power to the circuit.

Incase of Oil tankers, substantial charge buildup if any, used to be dissipated using bonding wires connected when the ship berths(સૂવાની જગ્યા) at an oil terminal. But since 2007/8 most new ships are built with self bonding cargo manifold that dissipate any residue charge through steel bolts the bite into shore loading arms.

Automobiles such as cars also work along same lines. The cars acts as a Faraday cage with electricals earthed to the shell. Even in case of a lightning strike you are safe inside a car rather than outside it.

Aircraft can build up massive charges flying through thunderstorm or even otherwise. All aircraft have Wire like attachments to their wings & flaps called Static Wicks that help dissipate charge while flying. Also bonding wires are used when the craft is on ground especially during fuelling. Grounding is the reason why a bonding wire is first lowered from an helicopter before winching((ચઢાણ ચડાવવાનો)) people aboard.

Thus, to avoid appliances or other electric devices giving a shock, the outer part of the appliance is connected to ground with a wire. That way, if something goes wrong inside, a person will not get a shock. Airplanes are usually made of metal, so the metal frame is used as a  conducting "ground" for all the electrical components inside the aircraft. So "ground" on an airplane is usually the frame. A metal frame also protects the occupants from lightning strikes. Parts of the aircraft that are made of plastics or composites are protected with a metal mesh or fibers. 

The aircraft itself becomes charged as it is flying. Snow, dust and rain, as well as ionization of the air by the engines, can cause the airplane to develop a static charge up to several million volts. Because the passengers and the equipment is inside the metal shell, there is little noticeable effect other than communications. Communications are disrupted by the radio frequency static that occurs when corona discharge or electrical leakage occurs.