Aye, I was certainly picturing a ship. I’m sure that’s been pointed out to me at least once in the past…
On closer inspection, OP seems to be enough of an enthusiast to come up with new terms, because neither “gunship” nor 戦艦 are actually on WaniKani. 
“Gunship” in Japanese, incidentally, is ガンシップ, while “gunboat” is 砲艦.