BeginnerSurvival
How to tame a nautilus and get nautilus armor in Minecraft
a Pufferfish or a Bucket of Pufferfish.
Tested 26.3

The Bucket of Pufferfish holds a fish that still puffs up and poisons when released, and wandering traders sell it. This bucket holds a small water mob together with its water. All mob buckets work the same; the Bucket of Tropical Fish page explains them.
This item has no crafting recipe.
a Pufferfish or a Bucket of Pufferfish.
Sold by Wandering Trader.
It carries a water mob so you can release it elsewhere. Spawns: Pufferfish. Animals that eat it: Nautilus.
No: only one per inventory slot.
Tactical Fishing (Catch a Fish... without a Fishing Rod!).