Why End On A Boat?

I think R and G's death ended on a boat because they had no purpose in life and when you are at sea you are nowhere. You are not at a certain point or in a certain country, you are just in the middle of nowhere. They were trying to find a purpose in their life but instead they end up dying in the middle of the sea. They were not important enough to wait to kill them until they reached England so people could watch, instead they were just hung on a boat with just some of the seamen watching. They had no destination and no purpose in life so the same with their death.