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

The Bucket carries liquids: use it on water or lava to pick up the source block, and use it again to place it somewhere else. It also collects milk from cows and goats and catches fish and other small creatures.
It is made with the Crafting Table from 3 × Iron Ingot.
An empty Bucket becomes a Water Bucket, a Lava Bucket, a Powder Snow Bucket or, used on a cow, a goat or a mooshroom, a Milk Bucket. Drinking milk removes all your status effects. A Lava Bucket is also one of the longest lasting furnace fuels.
A Water Bucket used on cod, salmon, a tropical fish, a pufferfish, an axolotl or a tadpole puts the creature inside, so you can carry it to an aquarium. An empty Bucket can also scoop up a Sulfur Cube.
A water bucket is also a survival tool: placing water just before landing cancels fall damage. Empty buckets stack up to 16.
3 × Iron Ingot → Bucket
// Slots with several items cycle through every accepted option.
a Pufferfish or a Bucket of Pufferfish.
Shield (6 Planks and 1 Iron Ingot) and Bucket (3 ingots), to block arrows and carry water.
At the Crafting Table: 3 × Iron Ingot give 1 × Bucket. It can be found as loot in Abandoned Camp, Woodland Mansion, Trial Chambers and Village.
It picks up and places water, lava and powder snow, collects milk and carries fish, axolotls and tadpoles. Use it on: Cow and Goat.
Yes, up to 16 per slot (most items stack to 64).