These are the kind of animals that scare children away from swimming pools. They're frightening and have full-body braille tattoos that scream, "I will chew through your calves!"
You could picture these brutes gnawing through the filter of a swimming pool, and attacking the toes of summer swimmers. As you slipped under, you'd find drowning a suitable alternative to the excruciating nibbling. The lifeguard couldn't save you. Nobody could. Because there's no match for underwater evil.
Thankfully, they're not in your local swimming pool, but they're in your local ocean. A sopping place that pours salt in your every wound. The next time you're deep in the ocean and you see a picture of these creatures, just remember to respect the oogly eyes and pointy teeth of underwater evil. Your calves will thank you.