Zombie Nautilus
Zombie Nautilus is an undead aquatic mob that always spawns with a trident-wielding drowned riding on its back — a pairing known as a zombie nautilus jockey. While mounted, the drowned takes complete control of the Zombie Nautilus's movement. Once the rider is dismounted or defeated, the Zombie Nautilus turns neutral, giving players an opportunity to tame and ride it themselves. Those appearing in warm ocean biomes display a distinctive coral-covered look that sets them apart from typical variants.
As an undead creature, the Zombie Nautilus burns in direct sunlight rather than suffocating when out of water, which distinguishes it from regular nautiluses. It attacks by dashing into targets and remains neutral unless provoked while untamed. Any player holding fish or a bucket of fish within roughly ten blocks will draw the Zombie Nautilus toward them. In Bedrock Edition, adult and baby drowned that collide with an untamed Zombie Nautilus can mount it and commandeer its movement. The mob counts toward the hostile mob cap and may despawn before a player first interacts with it, after which it becomes persistent.
Taming a Zombie Nautilus involves feeding it pufferfish or buckets of pufferfish, each attempt having a one-in-three chance of success. Once tamed, it can be fitted with a saddle for riding or equipped with nautilus armor for protection, and it may be leashed when not being ridden. Unlike standard nautiluses, the Zombie Nautilus cannot be bred. Killing one yields rotten flesh and a small amount of experience.