In World War II they had a gun mounted on merchant ships and I think a military gunner aboard.
Probably wouldn't be a bad idea today.
Yes, merchant ships wer armed.
Nice shot of somebody sitting on a Liberty Ship's deck gun.
http://ontour.blogs.com/photos/san_francisco/david_on_liberty_ship_at_san_fran2.html
And
http://ontour.blogs.com/photos/san_francisco/jonathan_trying_to_remember_boy_scout_tr.html
http://www.usmm.org/libertyships.html
Libertys carried a crew of about 44 and 12 to 25 Naval Armed Guard. Some were armed with:
One 4 inch stern gun
Two 37 mm bow guns
Six 20 mm machine guns
http://www.cr.nps.gov/nr/twhp/wwwlps/lessons/116liberty_victory_ships/116facts2.htm
Victory ships typically carried a crew of 62 civilian merchant sailors and 28 naval personnel to operate defensive guns and communications equipment. The crew quarters were located amidships. The Victory ships were different from the Liberty ships primarily in propulsion, the steam engine of the Liberty giving way to the more modern, faster steam turbine.
right about the armed ships of ww2---they called the gun crews US Navy 'armed guard'--the merchant marine crews got the high risk pay and the 'swabbies' had to settle for 21-30 bucks a month even tho' the risks were equal but no one wants to talk about that--ww2 naval service vet