With their bulbous, blobby, tasseled, warty or weedy appearance, frogfish are easily some of the strangest and most fascinating fish in the ocean. And to the untrained eye, they can be some of the hardest to find. These unusual fish are masters of disguise, so divers often swim right past them thinking they’re just another lump of sponge or blob of algae clinging to the reef. But once you know what to look for, their eyes, downturned mouths and leglike fins can give them away.

Scientists once thought there were well over 100 different species of frogfish, but they’ve since realized there are only around 50. The exact number is still unclear, however, because frogfish have a chameleonlike ability to change their appearance to fit their surroundings, so it can be hard to classify them. Unlike chameleons or octopuses, frogfish can’t change colors or textures quickly — it takes them a few weeks to blend into a new background.

Frogfish use their uncanny camouflage skills to get the jump — literally — on dinner. But that’s not their only hunting tactic. As highly effective ambush predators, they use a two-pronged approach. Blending into a reef lets them hide in plain sight, but frogfish are also a type of anglerfish. Their dorsal fin contains a retractable appendage that dangles like a lure above their mouth to attract unsuspecting prey. If a fish manages to eat the lure, the frogfish can regenerate a new one.

Once a frogfish catches the attention of its potential prey, it will continue to wiggle and bounce its lure until the creature comes within a few inches of its mouth. Then, in a split second, the frogfish goes from stationary lump to snapping jaws. They use a feeding technique called prey engulfment, like angel sharks and stonefish, to swallow their meals whole. When it strikes, a frogfish’s mouth can expand to about 12 times its normal size, and the lightning-fast snap of its jaw — about 6 milliseconds, the fastest of any vertebrate — creates a vortex that sucks the prey into its mouth.

Divers might not see frogfish on every dive, but that doesn’t mean they’re not around. In fact, frogfish are relatively common and live in warm, tropical waters all over the world, from the Caribbean to the South Pacific. However, if you’re keen to spot as many species as possible, Indonesia has the greatest diversity of frogfish, especially in the critter-rich waters around Lembeh Strait, which is home to at least nine species.

FAST FACTS

VARIATIONS
There are about 50 different species of frogfish, yet individuals from the same species can look different because they change their colors and textures to fit their surroundings.

WHERE TO FIND THEM
Frogfish are found throughout the world’s tropical regions, but the waters around Indonesia have the greatest diversity of species.

FUN FACT
Frogfish have no swim bladder, so they often use their pectoral fins to walk along the reef or seafloor.