The phrase denotes a concept of political geography and international law that a nation's maritime boundary should reflect the 'natural prolongation' of where its land territory reaches the coast.
Oceanographic descriptions of the land mass under coastal waters became conflated and confused with criteria that are deemed relevant in border delimitation.
[1] The concept was developed in the process of settling disputes if the borders of adjacent nations were located on a contiguous continental shelf.
[4] The relevance and importance of natural prolongation as a factor in delimitation disputes and agreements has declined during the period in which international acceptance of UNCLOS III has expanded.
[5] The Malta/Libya Case[6] in 1985 is marked as the eventual demise of the natural prolongation principle being used in delimiting between adjoining national maritime boundaries.