The continental shelf has been defined in a number of ways. It can mean the area of relatively shallow water that fringes a continent from the shoreline to the top of the continental slope. The top of the continental slope is often defined by the 200 m isobath. Continental shelf may also be defined as the maritime zone to include the continental shelf where it extends beyond the limit of the Exclusive Economic Zone to the limit of the continental margin. This area is also sometimes referred to as the ‘extended continental shelf’, and its limit is determined by the United Nations Commission on the Limits of the Continental Shelf.