The Net Dolphins(망돌고래,mangdolgorae, net dol-whale, net dolphin) is a creature found in The Second Floor of the Tower that specialise in fishing. They gather fish for their queen the Net Dolphin Madame. They do this using their special ability to manipulate Shinsoo to create a net within the water. They use the net to transport the various aquatic animals directly to the queen's mouth. While they are doing this, they are hunted by Dogs and the Bull.
Notes and Trivia
Mangdol Whale is a mistranslation. "Mangdolgorae"(망돌고래): "mang" means "net", "dolgorae" means "dolphin". However, 고래(gorae) means whale. Dol(돌) means many things like "stone" and so on.
By adding dol(돌) to gorae(고래), the term "whale" becomes "dolphin"(dol-whale).
This can be seen by the fact they all look like bottle-nosed dolphins, than whales.