Watercrafts
Watercrafts are divided into two different types: surface vessels and underwater vessels.
Surface Vessels
Surface Vessels, such as ships and boats, float ontop of the ocean. Ships usually have three main parts. The keel is the backbone of the ship, running along the center of the ship. The hull is the shell that protects the ship from water. The deck is the floor of the ship. Modern ships have multideck designs, with varying usage of these fundamental parts to create bigger and better ships.
Generally, ships also have two considerations based on the type of usage. If a ship is being used for transport, they must prioritze comfort features: wastewater treatment, water supply, passenger comfort, open-air design features. Furthermore, the ship must be still in weather, and designed to minimize unwanted movement. However, if the purpose of the ship is for cargo, then the ship must maximize space usage.
Energy
Due to the surface design, energy and thrust can use the surronding atmosphere. Most ships use diesel engines, using heavy fuel oil or marine diesel oil; for propulsion. There are three main types of propulsion mechanisms.
Direct Drive
DD mechanisms is where the diesel engine drives a crankshaft connected to the propeller, via gears. This option also allows someone to use a shaft-generator to create electricity. However, these generators can only be used while the ship is moving.
Diesel Electric
DE is a design used by many modern ships. In this option, the diesel crankshaft drives an electric generator, which is then used to power electric motors of the propellers. This allows for the direct usage of electricty for electrical needs, and is the preferred option for cruise ships.
Gas Turbine
A lesser known alternative, GT uses gas to drive a turbine, which is an environmentally friendly option.
Buoyancy
To remain ontop of the water, a ship must have buoyancy. The air inside of a ship is significantly less dense than water, and a ship must displace more water then the ship itself weighs to remain afloat. The air inside of a ship reduces the ships average density, and if it is less than water, the ship floats. Generally, the ship has a waterline marked on the hull. Anything above that waterline that is watertight is the Reserve Buoyancy, and can be used in case of an emergency, such as a leak.
Underwater Vessels
These vessels are ones that go underwater, including submarines. Submarines are fully encased vehicles that transport people or other items underwater. Due to the presence of being encased in water, submarines have several more design features they must incorporate, including life support features, oxygen production, energy production without oxygen, and emergency systems. Without oxygen, submarines are basically in a space-like atmosphere. However, space would cause rapid decompression in the event of a leak. Water, on the other hand, is considerably more dangerous: it can cause rapid compression and implosion if a leak is not stopped or poor design features are implemented (see OceanGate Submersible Implosion).
Energy
Due to being underwater, energy needs are more complex. Earlier designs of submarines used Stirling Engines or batteries that were recharged when the submarine surfaced. However, these designs inhibit a submarine from remaining underwater fully. Most submarines, therefore, use Nuclear ReactorNuclear ReactorIn it's most simplest form, a nuclear reactor uses Uranium and other radioactive materials and the fission from uranium to create heat, and transfer that heat into steam to create power. Nuclear reactors are one of the biggest sources of energy, although not renewable, uranium has a very high energy density resulting in massive power transmissions. There are many different types of nuclear reactors, and this term serves as a broad hub/introduction for each type. After uranium is used in reactos for energy production. Nuclear submarines can operate for decades without refueling, requiring stops for only food for the crew, and other necessities. Reactors are also significantly more silent than diesel engines, and the main noise generation is by the cooling pumps and other required machinery. However, modern designs include advanced insulation and other methods to reduce noise generation.
Acoustic Stealth
Submarines are mainly used by the military, barring smaller versions for research purposes. However, these must be silent, to avoid a target from finding them. Modern sonar systems are highly advanced, and can detect acoustic noise well. However, the ocean is not silent, and it gives submarines buffer room. The main point in acoustic stealth is to blend in.