Features

Butterfly Fish: Passive (replaces Witch)
Lionfish: Aggressive towards players and fish, poisonous (replaces Zombie)
Stone Fish: Aggressive, poisonous (replaces Husk)
Jellyfish: Attacks fish and players, poisonous (replaces Cows)
Shrimp: Passive (replaces Pig)
Sharks: Hostile toward players, fish and sheep (replaces Guardian & Elder Guardian)
Crabs: Attacks players and fish (replaces Spider & Cave Spider)
Octopuses: Hostile, attacks players and fish (replaces Skeleton & Stray)
Whales: Passive, attacks fish and shrimp (replaces Polar Bear)
Mantarrayas: Passive, attacks fish (replaces Evoker)
Piranhas: Hostile towards players and other mobs (replaces Silverfish)
Swordfish: Attacks players and fish (replaces Zombie Pigman)

Creators Twitter; twitter.com/8Fernancraft