Crawdad

Crawdads are enemies found in the Cavern layer. They act like Crabs, walking along the ground and jumping at the player when in close enough proximity, though they are slightly faster. They are also capable of moving through water unhindered.

Crawdads are unique in that their ability to spawn is connected to two other enemies: the Salamander and the Giant Shelly. Of these three enemies, a world will choose two types that it can spawn, leaving the third inaccessible. Crawdads will never spawn in a world that features both Salamanders and Giant Shellies together.

Trivia

 * Like their "alternates" mentioned above, Crawdads have multiple colored variants, with different sprites but identical stats and behavior.
 * In real life crawdads, also called, are a type of small, freshwater lobster. Real life crawdads generally grow to a little over half a foot long, and as such do not pose any significant threat to humans, unlike Terrarian crawdads.

History
Crabisse 가재 龙虾