Sis forStern (ship)
A submarine is a seafaring vessel that can completely submerge for long periods of time. Some submarines can stay under water for 6 months at a time. Submarines are used for exploring, and by the Navy.
Wis forWake (water)
A wake is a mark made on the surface of the water by a fast moving object like a boat. The wake is made by the water being pushed out of the way as the boat passes through, and the size of the wave can be very large for a large, fast-moving boat. Small things like ducks will also leave a wake as they swim across water.
A yacht is a type of fast sailing boat. Sailboats do not have engines or motors, they move because the wind blows them along.