At least 11 species of fish can walk on land or along the seafloor, and several more use their fins to crawl, climb, or “crutch” their way across solid surfaces. These aren’t oddities from the deep past. They’re living species found in mangrove swamps, coral reefs, cave systems, and tropical waterways around the world. The list spans mudskippers, walking catfish, hillstream loaches, epaulette sharks, killifish, and several types of skates and frogfish.
Mudskippers: The Classic Land Walkers
Mudskippers are the most recognizable walking fish and the ones most people picture when they hear the term. Found across tropical mudflats in Africa, Asia, and Australia, they spend significant portions of their day out of water, using a movement called “crutching.” Both pectoral fins plant on the ground simultaneously, lift and vault the front half of the body forward, and the fish lands on its smaller pelvic fins while the tail drags behind. Then the pectoral fins swing forward to start the next stride. It looks remarkably like someone moving on a pair of crutches.
This ability isn’t accidental. Mudskippers that live on land have noticeably different skeletons from their more aquatic relatives. Their pectoral fins are longer, with thicker bones and enlarged attachment points for muscles. The shoulder girdle is reinforced with extra bone density to handle the stress of supporting body weight against gravity. A specialized notch in the shoulder bone, found only in the more terrestrial species, gives the fin joint a wider range of motion. These aren’t subtle differences. When researchers compared land-dwelling and water-dwelling mudskipper species using skeletal measurements, every bone structure in the pectoral fin was significantly longer and wider in the terrestrial group.
Mudskippers breathe on land by absorbing oxygen through their skin and the lining of their mouth, which they keep moist by rolling in mud. They can survive out of water for extended periods as long as they stay damp.
The Cave Angel Fish
Perhaps the most surprising walker is a small, blind cavefish from Thailand called the cave angel fish (Cryptotora thamicola). It doesn’t just walk on flat ground. It climbs waterfalls. Researchers discovered that this fish moves with a salamander-like gait, alternating diagonal pairs of fins the same way a lizard alternates its legs. No other living fish walks quite like this.
What makes it possible is a pelvis that looks startlingly like a land animal’s. The cave angel fish has a robust pelvic girdle physically connected to its spine, providing the structural support needed to hold its body weight against gravity and anchor the muscles used for walking. This feature is otherwise associated with four-legged land vertebrates, not fish. Based on CT scans of the cave angel fish’s unusual skeleton, an international team at the Florida Museum of Natural History identified 10 other hillstream loach species that share a similarly hefty pelvic structure, suggesting they may also be capable of walking. At least one of those species, Homaloptera bilineata, has been observed using its fins to propel itself forward on solid surfaces.
Epaulette Sharks
Nine species of epaulette shark, small reef-dwelling sharks in the genus Hemiscyllium, walk along the ocean floor using their pectoral and pelvic fins. They rotate each fin in sequence, stepping forward in a pattern that looks more like a slow trot than a swim. These sharks live on coral reef flats in the Indo-Pacific, where outgoing tides can strand them in shallow, isolated tidepools.
Epaulette sharks have two distinct walking speeds. At slower speeds (under about 4.5 centimeters per second), they use a symmetrical trot with diagonal stepping, bending their bodies in a standing wave while their fins rotate in a coordinated pattern. At faster speeds, roughly 4.5 to 8 centimeters per second, the body produces a traveling wave and the fin steps become more frequent, transitioning toward swimming. During slow walking, the pelvic fins do most of the heavy lifting, showing the greatest range of motion and spending about 5% more time in contact with the substrate than the pectoral fins.
These sharks can also tolerate extremely low oxygen levels. When the tide drops and pools become hypoxic, epaulette sharks suppress their metabolism and shift to energy pathways that don’t require oxygen. This lets them survive conditions that would kill most other sharks, giving them time to walk between tidepools or wait for the tide to return.
Walking Catfish and Snakeheads
Walking catfish (Clarias batrachus) are notorious for their ability to cross dry land, sometimes traveling between ponds or drainage ditches during rainy nights. They wriggle forward using serpentine body movements while propping themselves on stiffened pectoral fin spines. They’re an invasive species in Florida, where their overland migrations alarmed biologists in the 1960s.
What keeps them alive on land is a specialized breathing organ called a dendritic organ, a branching, tree-like structure located in a chamber above the gills. It’s covered in a thin, heavily vascularized membrane that works like a primitive lung, absorbing oxygen directly from air. The structure is supported by cartilage, which keeps it from collapsing when the fish is out of water, unlike regular gills that flatten without water to buoy them. A similar structure, called the labyrinth organ, is found in climbing gouramis and other fish in the anabantoid group. These plate-like organs sit in a separate chamber above the gills and are covered in respiratory tissue that extracts oxygen from gulped air.
Killifish and Other Amphibious Species
The mangrove killifish (Kryptolebias marmoratus) lives in ephemeral pools and crab burrows throughout mangrove swamps in the tropical western Atlantic. It regularly leaves water to escape low-oxygen conditions, but also to hunt, disperse to new habitats, and even reproduce. On land, it flips and launches itself using powerful tail movements rather than fin-based walking, but it navigates terrestrial landscapes effectively enough to find new pools. Research has shown that terrestrial exposure actually improves spatial learning in this species, suggesting the brain adapts to the demands of navigating two very different environments.
Other amphibious fish, including certain blennies that live in the intertidal zone, become air-exposed when the tide drops and use fin movements and body undulations to move across rocks. Their motivations are similar: escaping poor water conditions, finding food, or simply dealing with a habitat that regularly dries out.
Underwater Walkers
Not all walking fish leave the water. Several species “walk” exclusively along the seafloor. Skates in the order Rajiformes use specialized two-lobed pelvic fins to punt themselves forward along the bottom. Frogfish creep along coral and sponges using pectoral fins that have evolved to look and function almost like stubby arms, grasping surfaces and pulling themselves forward one slow step at a time. Sea robins fan out modified pectoral fin rays that function as separate “legs,” probing the sand for food as they stroll along the bottom.
These underwater walkers face different challenges than their land-going relatives. Buoyancy offsets most of their body weight, so their skeletons don’t need the same reinforcement. Instead, their adaptations center on fine motor control, letting them move precisely through complex environments like coral reefs or rocky rubble where swimming would be clumsy.
Why Walking Evolved
Fish walk for practical reasons. The most common trigger is escaping unfavorable water, particularly low-oxygen conditions caused by stagnant water, receding tides, or overcrowded pools. Walking lets a fish reach better habitat when its current pool is failing. For reef-dwelling species like epaulette sharks, walking solves a specific tidal problem: getting between isolated pools without fully swimming. For cave angel fish, walking and climbing lets them move upstream through fast-flowing cave systems where swimming against the current would be impossible.
These living species also offer a window into one of the biggest events in evolutionary history. Around 375 million years ago, during the Devonian period, the first vertebrates began transitioning from water to land. Early tetrapods like Ichthyostega may have used a forelimb-driven crutching gait similar to what mudskippers use today. Fossil evidence suggests the earliest limbed vertebrates initially evolved their limbs for interacting with underwater surfaces, with specializations for supporting body weight on land appearing later. The competing demands of aquatic and terrestrial environments likely produced a locomotor style unlike anything alive today, but modern walking fish give researchers a living laboratory for understanding how fins became legs.