Zombie Nautilus

A zombie nautilus is an undead variant of the nautilus that spawns being ridden and controlled by a trident-wielding drowned, forming a zombie nautilus jockey. Once separated from the jockey, it behaves like a regular nautilus, but burns in sunlight instead of suffocating while not in water.

When an adult drowned spawns outside of river or frozen river biomes, (excluding drowned reinforcements) either naturally or as part of a structure (i.e. an underwater ruin), and is wielding a trident in its main hand, it has a 50% chance to spawn as a zombie nautilus jockey, riding a zombie nautilus. Zombie nautilus jockeys thus spawn in dripstone caves and various ocean biomes; those that spawn in warm oceans will become the coral zombie nautilus variant, which only differs in appearance.

In this state, the zombie nautilus's movement is controlled by the jockey. When the drowned rider is dismounted or killed, the zombie nautilus becomes neutral. It can then subsequently be tamed and ridden by the player.