Zombie Merman

The Zombie Merman is a pre-Hardmode enemy that can be spawned by fishing in a Blood Moon. When the bobber dips and the player attempts to reel in a fish, a Zombie Merman or a Wandering Eye Fish has a chance to spawn within a few tiles of the bobber in place of a fish.

Tips

 * The Sonar Potion will detect if a Blood Moon enemy like the Zombie Merman is about to be hooked.
 * Using the Chum Caster will greatly increase the chances of hooking Blood Moon enemies.
 * The Zombie Merman has high health and defense, moves very quickly, and does not take knockback, making it a challenging enemy for underpowered characters.
 * It is very agile while in water, making it hard to deal with. Players can build a layer of platforms above their fishing spot to prevent the Zombie Merman from entering the water in the first place.
 * The Zombie Merman is a great way of progressing in the early game as it can drop useful items.

Trivia

 * The Zombie Merman Banner is the last item in alphabetical order out of all the items in Terraria.
 * It resembles both the Icy Merman and the Merfolk form that the player can achieve by equipping the Neptune's Shell (or its derivative accessories) in water.