Nautilus

The Nautilus is a passive mob added by Upgrade Aquatic. They are found in underwater caves and ravines, but cannot be found in cold or frozen oceans. Nautilus buckets can be purchased from the Wandering Trader.

Behavior
Nautiluses bob up and down and dash randomly, leaving a bubble trail when they do. When approached by a player, Drowned, or Squid, or if they are hit they will perform a few dashes to escape. Additionally, Nautiluses are immune to bubble columns and are unaffected by their pull. Nautiluses released from a Bucket will not despawn.

Drops
The Nautilus always drops one Nautilus Shell and can be captured in a Bucket.