In a new short story one of mine, of the main characters speaks French with English as a second language. As a result his English grammar tends to be 'pigeon' if you get what I mean? In one of his dialogues he uses the phrase, "...for the sea; she is a cruel mistress sometimes!" Now, I'm using a semi-colon here but is that the correct style of punctuation? Would a comma, or a dash work equally well?
A semicolon is correct. A dash would be fine. A comma would, IMO, be incorrect. I see commas used like this quite frequently in published books, but I tend to assume that they're explained by Americans having a terror of semicolons.
The term for a simplified, blended language like that is a pidgin. A semicolon is not appropriate in the above dialogie fragment. You should use a comma.
I was going to ask why a semicolon was incorrect, and realized I've probably misunderstood the example. I thought that the example was cutting off a complete initial sentence because it wasn't relevant to the question, but that in the original work it would be a complete sentence. That is, I was thinking of something like: "I'll do anything for the sea; she is a cruel mistress sometimes!" Is the entire thought instead, "For the sea, she is a cruel mistress sometimes!" In that case, yep, I was wrong about the semicolon.