Sea Emperor

The Sea Emperor is a Sea Creature that can appear while Fishing once a player's  level is 20 or higher.

It is level 150 and has

Drops

 * Emperor's Skull
 * Shredder
 * Raw Fish
 * Lily Pad
 * Sponge
 * Enchanted Lily Pad
 * Enchanted Prismarine Crystals
 * Enchanted Prismarine Shard
 * Fishing Exp Boost
 * Flying Fish Pet

Trivia

 * Despite the Sea Creature Guide referring to this creature as Sea Emperor, it's in game name reads instead as The Emperor.
 * There was a bug with the Ink Wand's ability Ink Bomb and the Explosive Bow's explosive arrows, where if the Sea Emperor is killed by either of these it can drop multiple skulls and have a higher drop chance of rare items. This is because the Sea Emperor is technically two mobs, and the ability kills both of them at once, causing double drops. This was fixed in the Community Update, patch 0.9.
 * The Sea Emperor always targets other players first before targeting you, making it dangerous when you are fishing with other people