The novel is primarily set on the English coast, and an intriguing aspect to the novel is that it never defines which one (England, being on an island, has several.) As Charles repeatedly mentions the expanse of sea visible before him without any indication that France or Europe are on the other side of it (which he might conceivably do if he were on the east or south coasts,) the implication is that he's on the west coast, facing the Atlantic Ocean.