Fishermerms are passive Mobs found in Marsh biomes in the Shipwrecked DLC. They spawn from Fishermerm's Huts in Merm Villages. Unlike Merms, they are passive creatures and will not attack the player even if provoked. They periodically fish out Tropical Fishes at Tidal Pools, though they do not eat what they catch and simply leave it on the ground. When spotting a player they will run away in random directions in the opposite direction of the player.
Below is the number of hits it takes with each weapon to kill a Merm/Fishermerm when playing with characters with a default damage modifier. The Weather Pain is not included due to the random nature of its projectile.