Shipwrecks to me seem underdeveloped, and easy to loot, few mobs around to protect it at times. The ocean is still a brand new opportunity for new enemies, and what better structure to improve than shipwrecks? Undead Pirates can be an amazing addition to the ruins, and be another mob to use swords. They would spawn in shipwrecks found in the ocean biome, usually on or around the ship. They are hostile mobs, and will immediately attack the player using a sword of some type, likely iron to provide some challenge. They will not be able to swim like the Drowned. Likely would drop some gold nuggets, and rare occasion golden ingots. They would be a variant of the skeleton, wearing ruined pirate outfits and maybe a hat.