Its a Submarine shaped like a Sub Sandwich, what else did you expect?

From Wikipedia:

A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as "boats" rather than "ships" irrespective of their size.

Also from Wikipedia:

A submarine sandwich, commonly known as a sub (North American English), hoagie (Philadelphia metropolitan area and Western Pennsylvania English), hero (New York City English), Italian (Maine English), grinder (New England English), or a spuckie (Boston English), is a type of cold or hot sandwich made from a cylindrical bread roll split lengthwise and filled with meats, cheeses, vegetables, and condiments.[2][3] It has many different names.[2][1]