Why is it we say she when referring to a ship?

Answer 1

The reason a ship is referred to in the feminine dates back a long way in naval tradition. Its actual origin is unclear.

From a shoppe window in San Francisco (via the Gray Monk):

A ship is called a 'she' because:

there is always a great deal of bustle around her;

there is usually a gang of men about, she has a waist and stays;

it takes a lot of paint to keep her good looking;

it is not the initial expense that breaks you, it is the upkeep;

she can be all decked out;

it takes an experienced man to handle her correctly;

and without a man at the helm, she is absolutely uncontrollable: she shows her topsides, hides her bottom and, when coming into port, always heads for the buoys....

Answer 2

Most things are referred to as 'she.' Boats, cars, even "sister cities." Men form attachments to objects and consider them feminine because it sets them at a different level than a man.