Fathom was originally a land measuring term derived from the Ango-Saxon word "faetm" meaning to embrace.
In those days, most measurements were based on average size of parts of the body, such as the hand (horses are still measured this way) or the foot (that's why 12 inches are so named).
A fathom is the average distance from fingertip to fingertip of the outstretched arms of a man — about six feet. Since a man stretches out his arms to embrace his sweetheart, Britain's Parliament declared that distance be called a "fathom" and it be a unit of measure. A fathom remains six feet.
The word was also used to describe taking the measure or "to fathom" something. Today, of course, when one is trying to figure something out, they are trying to "fathom" it.
Naval Coastal Battery is the branch of armed forces concerned with operating anti-ship artillery or fixed gun batteries in coastal fortifications. It was also used as observation posts for soldiers who guarded the harbour.
It has been held as a general rule of thumb, that one shore-based gun equalled three naval guns of the same calibre, due to the steadiness of the coastal gun which allowed for significantly higher accuracy than their sea-mounted counterparts. Land-based guns also benefited in most cases from the protection of walls or earth mounds which gave the guns an added measure of protection.
The use of coastal artillery expanded during the Age of Discoveries, in the 16th century; when a colonial power took over an overseas territory, one of their first tasks was to build a coastal fortress, both to deter rival naval powers and to subjugate the natives. The Port Siloso at Sentosa is an excellent example of a widely used coastal fort which mounted defensive artillery, in this case muzzle-loading cannon. During the 19th century China also built hundreds of coastal fortresses in an attempt to counter Western naval threats.
Three Mile Limit
The original three-mile limit was the recognized distance from a nation's shore over which that nation had jurisdiction. This border of international waters or the "high seas" was established because, at the time this international law was established, three miles was the longest range of any nation's most powerful guns, and therefore, the limit from shore batteries at which they could enforce their laws. (International law and the 1988 Territorial Sea Proclamation established the "high seas" border at the 12-mile limit.)
