You nailed the pulpy premise. The writing is excellent. Really imaginative creatures and NPCs! And it looks nice, too.
I was a little confused about what was going on spatially--since you used a flowchart/diagram style pointcrawl, a sentence up top that simply explains *what* location we're exploring would have really helped me.
Like, "the strange submersible ship has crashed into a lighthouse, and is beached and exposed. You're going in to look for treasure." But I think I mostly understood after reading the whole thing and this seems like it would be a blast to play.