A cape is a small peninsula or strip of land that sticks out into a body of water, often a relatively high piece of land called a headland. For example, the Cape of Good Hope in South Africa is a cape on the Atlantic ocean.
There is a small headland in west Cornwall called Cape Cornwall. The cape is located right in the southwest of England and is a popular holiday destination for Britons and foreigners alike.
The water in the bay is quite calm because it is protected from the ocean currents by the cape, which sticks out and separates the bay from the ocean.
A cape is also a type of clothing. In this sense it is like a coat with no sleeves that mostly covers the back but not the front half of a person. They were more popular in the 18th and 19th centuries, but often appear in literature or films about those times, or about superheroes. Batman and Superman both wear capes, for example.
The strange, very beautiful and attractive woman arrived at the party all by herself and wore a bright red cape, which covered her shoulders and back but left her front and arms bare, so it can't have been very warm.