If you’re looking to find one of the strangest fish in the sea, look no further than the frogfish.

Their leg-like fins, camouflaged skin and perpetual “oh no!” expressions make them an unusual sight on the sea floor. But, if you’re lucky enough to spot one in person, you’ll see why they’re a favorite of scuba divers and underwater photographers alike. Read on to see what makes the frogfish so weird—and wonderful.

So, what are frogfish?

Frogfish are any members of the family Antennariidae, a type of anglerfish that includes about 50 species. They’re found in shallow tropical and subtropical ocean waters around the world and are fairly small—the biggest species only grows to 12 in (30 cm) long. They have modified pectoral fins that resemble legs, which allow them to “walk” along the ocean floor looking for prey.

Frogfish are masters of disguise—they use various type of camouflage to hide from predators and sneak up on prey. Some species resemble the colors and textures of sponges. The Commerson’s frogfish (Antennarius commerson), for example, can change its color to blend in with pink, red, yellow or brown sponges and rocks, and even has unevenly-textured skin that matches the rough surface of the reef. The psychedelic frogfish (Histiophryne psychedelica) has yellow, brown and white stripes that look just like stony corals. And the hairy frogfish (Antennarius striatus) has long, waving appendages that can resemble algae or even a spiny urchin.

This camouflage is a type of aggressive mimicry—a strategy of resembling something else to gain an advantage over your prey. This means potential prey, like small fish or crustaceans, can swim by and never see the well-hidden frogfish, allowing them to attack the prey from a close range. This technique is also seen in animals such as the alligator snapping turtle, who resembles dead wood, and the antmimicking spider, who resembles, well…an ant.

Frogfish have another trick up their sleeves (fins?) for tricking prey into becoming dinner. Frogfish have a dangling lure, which is a type of modified fin called an illicium, that acts like a fishing rod for prey. It can resemble a worm, shrimp or even small fish that looks very tasty to other fish and crustaceans! Once the prey has drawn close enough to realize the “worm” isn’t really a “worm”…it’s probably too late. The strategy is also used by the frogfish’s cousin, the deep-sea anglerfish (of Finding Nemo fame).

Still not convinced that frogfish are some of the coolest fish out there? Check out this site, which has a complete list of frogfish (with photos!) and where to find them. Chances are, there are frogfish that live in a tropical ocean near you. Just make sure you look closely—that camouflage works on prey and divers alike!