Mershark

A race of mermaids with the characteristics of sharks. These monsters are extremely ferocious, just as they look, which is a rarity for the mermaid family since most of them have a docile disposition. They have excellent senses with which to detect humans, and they can accurately pinpoint the specific location of a man hiding in a ship. Because their senses are excessively keen, detecting a man's presence will even cause them to perceive a man's existence so incredibly strongly that they go wild with lust. If they discover a man who fell into the sea, they'll mercilessly snap at him and try to greedily devour the man's body. They don't actually consume such prey, but because of how they look when they attack humans, they are feared as "man-eating sharks". They have sharp fangs and strong jaws, and it's said that they are even capable of biting through iron chains and gnawing holes in the bottom of ships. On the other hand, since their fangs contain mamono mana and have the same properties as mamono realm silver, they do not injure humans. Those bitten have mana spill out from inside their body instead of blood, and when a man's mana mixes with their mana, it becomes stained bright red; instead of a blood spray, a mana spray will stain the sea red.