The bigest advantage of carbon guns is that they are rigid, but still easy to manufacture in to different shapes. So you can have a very thin and wide gun that will not bow when you put 2-3 rubers on it.
As for ocean hunting, maby the bigger models like the c4 Urukay and Bleutec Oceanborn are better then low grade wooden guns, but they cost like the high grade wooden guns so it's a matter of prefrence. I'm not very experienced with open water hunting so I might be wrong on this one.
However, for catching smaller fish carbon guns can be made very manuvarable while retaining rigidity, something that wooden and aluminium guns can't do. For example the pathos laser carbon can withstand 2*20 guns (it will kick back like a mule) without bending, while the similar diameter aluminium gun probably can't. I personaly prefer round barrel carbon guns for hunting in the surf,my favorite is the bleutec bastard but it's way to expensivem becouse they have a smaller diameter barrel and so they have less drag when turning them quickly into a wave.