I've actually gotten a few by fighting IN the ocean, but my AFK farm isn't getting me any at all. And it's set up right ON TOP of the ocean, with tons of water on each side of me. Is it because I've also placed my jungle blocks and now the jungle biome cancels out the ability to get pirate maps? I mean, I'm still getting sharks and jellyfish along with the jungle fish, but is there something I'm missing here? I've killed probably a thousand enemies and not one map.