https://www.curseforge.com/minecraft/mc-mods/pirates-and-looters-mod

(there called pirate bomber not gunner. Gunner is seprate mob)

It is a modification that diversifies the ocean. Adds several pirates to the game with new killing abilities. They are not normal illargers. They are very aggressive and there are skirmishes between them when one of them hits them with a bullet. In mod, you can also find pirate pistols and even a hand cannon! The mod is made by Mcreator however half the mod is coded (such as animations or combat systems)