That, my good sir, would count as sneaking. It would involve clinging to the outside hull, which shouldn't be too hard since metal is magnetic, and getting through a cannon port into the gun deck. The resulting thump would naturally attract the attention of our crawl-space gremlin and we'd have you.
Pictures you clinging to the side of the ship with magnets. Yes, that would work nicely.
I think the thing to do would be for you to write a post about how you came aboard and your discovery by @Shadow_Darksong.