Krakentilus

The Krakentilus boss is found hidden as a shell on the sea floor. It has four attacks: a charge, a whirling move, a drowning attack and a summoning of tentacles. A custom boss bar tracks its health during the fight, and defeating it drops a Krakentilus Shell. The shell can be worn as a chestplate, which gives 7 armor, 4 extra health and 40% more swimming speed.

Three Nautilus variants are added alongside the boss. The Puffer Nautilus has spikes and is tamed with raw fish, then ridden with a saddle and given a dash ability on the default key. The Creeper Nautilus is a rare hostile mob whose explosion deals less damage than a vanilla creeper, and it drops Wet Gunpowder. Wet TNT is crafted from Wet Gunpowder and releases water instead of exploding, and Shell Steel can be used to ignite it. Three spears can also be crafted.

Every player and the server need a copy of the mod. Files are published for Forge and NeoForge, covering 1.20.1 and 1.21.1, with build 1.108 as the latest file for both. The boss range and the time before an unattended encounter despawns, which is 8 minutes, can be changed in the config file. The license is All rights reserved, so the code is not open source.