Nautilus Shell

A nautilus shell is an item that is used for crafting conduits.

Fishing
Nautilus shells can be obtained as a 'treasure' item from fishing.

Drowned
3% or 8% of Drowned will spawn with a nautilus shell that will always be in their offhand, and they will always drop it when killed, since drowned always drop equipment in their offhand.

Trading
Wandering trader will sell nautilus shells for 5 emeralds each.

Treasure Chest
Nautilus shells can be obtained as an item from treasure chests.

Trivia

 * Nautiluses are animals, which occupy deep oceans in the real world. However, they seem to be absent in Minecraft, as there are currently no plans to add nautilus mobs into the game.

Issues
Nautilusschale Coquille de nautile 앵무조개 껍데기 Nautilusschelp Muszla łodzika Concha de Náutilo Раковина наутилуса Nautilus Shell 鹦鹉螺壳