We are at sea?

so lets recap Rosencrats and guildernstern are on there way to england on a boat and Hamlet replaces the letter with a fake one comdeming there lives. Now there both on a boat sailing to death, this could represent the fact that during shakephere's time America wasn't founded yet and if you sailed you would sail off the end of the world into nothign and die so all in all they were sailing to their deaths.