【Marine】 ,  【maritime】 ,  【nautical】 ,  【naval】  are not closely synonymous terms but they are so interrelated that they are sometimes a cause of confusion.

【Marine】  and  【maritime】  both imply a connection with the sea.

【Marine】 is the appropriate term when what is qualified is produced by or is found in the sea or in a body of salt water (for this sense see AQUATIC ) or is intended for use at sea or deals with the sea or with vessels that ply the sea or other large bodies of water.

【Marine】 is sometimes used also when there is an actual or implied reference to seamen and the term commonly applies to soldiers who serve at sea.

【Maritime】 is the appropriate term when the reference is to countries, climates, or peoples on the borders of a sea or to the navigation of or commerce on the seas.

But  【maritime】  and  【marine】  are sometimes used interchangeably, especially in reference to law and insurance.  【Nautical】  and  【naval】 , on the other hand, imply a connection with ships and shipping, and therefore only indirectly with the sea.

【Nautical】 , however, is the usual term in applications where a relationship to sailors or seamen or the sailing of ships or boats is distinctly implied.

【Nautical】 is usually the preferred term when reference to the art or profession of navigation is implied.

【Naval】 usually implies reference to a navy as distinguished from a merchant 【marine】 and as composed not only of ships, but of men, supplies, and armaments; at times, only from the context can a reader be sure whether ship or 【naval】 force is referred to.