I have an interview for an internship with the software/technology department of a large financial institution next week and during preparation, I came to ask to myself whether swearing in an interview would be a red flag? I don't mean swearing at people (e.g. interviewer), but rather to emphasize that I really loved working on *that* specific project, I would say "it was the absolutely f--ing best thing I ever did". I find the swear word adds an extra bit of emphasis and I would most likely use it outside of an interview. 

Would that be to casual? Should I see how easy-going the interviewer (a software engineer) is? Or should I just avoid it?

On the one hand I would like to be natural and would also like my future colleagues not to be uptight about things like this, though at the same time I also don't want to seem like a delinquent.