The Steampunk Boiler Room

Hi All!
I have a question about the weapons I would be looking at in this era. My main character in my NaNo novel has built a "Sinking Ship" (pre-cursor to a submarine, which I know dates back to the Civil War at least.... the Merimack and such), and he will use this to get where he is going....

But I'm not sure exactly what forms of weaponry will be acceptable. My thinking pattern right now seems to be more toward hand-to-hand combat... swords and shields and catpults and such. I know that is all much "older", but is that an acceptable method by which to do battle, or should I incorporate something(s) newer, etc.

Any help would be greatly appreciated!
Thanks,
Beck

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