can someone tell me what COX means in front of us navy, my great grand father severed in world war one but i cant fin anythin online

The coxswain (pronounced /ˈkɒksən/) is the person in charge of a boat, particularly its navigation and steering. The etymology of the word gives us a literal meaning of "boat servant" since it comes from cox, a coxboat or other small vessel kept aboard a ship, and swain, which can be rendered as boy, in authority.

the response is in Wikipedia

look for Cox's Navy in Wikipedia

thank you. i did find what i was looking for. but do you know if there is anyway to find out what ship that my g-grandfather was on?