Britain has a fine naval history which is reflected in more than just a few common phrases which sometimes get misunderstood. The following is a list of some of the more common ones.
Ship-shape and Bristol fashioned: In the days of the great sailing ships the British, being an island race, were particularly skilled at maritime design. British ships dominated the high seas globally. The best of the best were crafted rather than built, such was the quality of the shipwrights of the day, in Bristol. Therefore if anything is of superior quality and tidyness it is said to be "Ship-shaped, Bristol fashion."
Above Board and enough room to swing a cat: These two can be linked together in one explanation. The cat was a whip which was split into three at its tip and each of these strands was further split into three, so each lash inflicted nine strokes at once giving rise to the name "cat o' nine tails".
Any misdemeanour that was brought before the captain would possibly be punishble not by walking the plank - that's a total myth, after all why waste the manpower? - but by a lashing. In order that the punishment was seen to be done it was performed on the open top deck, or above board, where all could see. As well as that, it couldn't be done on the gun decks because there wasn't enough room to swing a cat.
Son of a gun: This one is debatable, but as I understand it in peacetime, when it wasn't considered so unlucky to have women on board ships, occasionally a woman would end up with child after an illicit liaison or two 
. The place that gave the most privacy for the birth of a child was on the gun deck, between the cannons. If the mother could not or would not name the father of the child the birth certificate would be filled in with the father's name as "A Gun".
The sun's over the yard arm: As in "The sun's over the yard arm, time for a snifter." This dates back to the days of the rum ration (actually that's only recently been revoked by the Royal Navy). Each seaman was entitled to beer and rum, especially on longer voyages as they may have been on the seas for weeks on end, but you couldn't drink what you were floating on as desalination systems hadn't been invented. This was doled out to the sailors from around lunchtime onwards. If the sun had not risen above the yardarm, the arm on the main mast which sticks out a yard, then it was deemed too early for the ration to be given.
Brass Monkeys: As in "cold enough to freeze the balls off a brass monkey."
Yet again this is debatable, but it's the most plausible explanation I've come across.
In the days of galleons and cannons, the cannonballs were stowed on trays called monkeys. These monkeys were made of brass in order for them a) to be slid easily over the wooden boards of the gun decks and b) not to spark against the cast iron cannonballs. Unfortunately in cold weather brass contracts more than cast iron, so as the temprature dropped the balls would fall off the brass monkeys.
And as they drew nearer I could hear them saying they'd rather be compared with goats, because they're nimble on their feet 'cuz of the mountains. 
has it all gone?
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