Bats can swim, but they are terrible at it. When a bat lands in water, whether by accident or misjudgment, it uses a labored, butterfly-like wing stroke to paddle across the surface. This is not a skill bats have evolved to use routinely; it is an emergency maneuver, and the animals look about as graceful doing it as you would expect from a creature whose entire body plan is optimized for flight. The relationship between bats and water is more interesting than the simple yes-or-no question suggests, because bats interact with water constantly during their lives without actually entering it.
What Swimming Actually Looks Like for a Bat
When a bat ends up on water, it does not sink immediately. Its body is light relative to its surface area, and the broad wing membranes provide some resistance against submersion, at least for a short time. The swimming motion is an exaggerated version of the flight stroke: the bat sweeps both wings forward and down against the water surface simultaneously, pulling itself along in a choppy, effortful crawl. The movement resembles a human butterfly stroke more than any other comparison, though far less coordinated. Each stroke lifts the bat’s head and chest slightly above the waterline before it settles back.
The pace is slow. A bat swimming across a pool or pond covers distance at a fraction of its flight speed, and the effort is enormous relative to the distance gained. Research on the energy costs of animal locomotion has shown that flying animals generally require substantially more energy per unit of movement compared to swimmers, and bats carry that inefficiency with them into the water, where they get none of the aerodynamic advantages their bodies were shaped for.1PubMed Central. Energy efficiency and allometry of movement of swimming and flying animals A bat in water is an aircraft trying to be a boat, and the energy budget reflects it.
Most observations of swimming bats involve animals that fell into pools, livestock troughs, or other calm bodies of water. The bat paddles toward the nearest edge, climbs out if a surface offers grip, and flies away. The entire episode rarely lasts more than a minute or two in good conditions. In smooth-walled pools or containers with no climbable edge, however, the story often ends differently: the bat exhausts itself and drowns.
Why Bats End Up in Water in the First Place
Bats are not blundering into ponds at random. They seek out water deliberately every night. Most insectivorous bats drink on the wing by swooping low over a calm water surface and dipping their lower jaw to scoop water as they pass. This maneuver is precise and practiced, but it requires the bat to fly very close to the surface at speed. A miscalculation, a gust of wind, or a moment of disorientation can turn a drinking pass into an unplanned splashdown.
Swimming pools are a particular hazard. Bats navigate partly by echolocation, and their brains appear to treat any extended, acoustically smooth surface as water. A study testing wild bats from 15 species across seven genera found that bats consistently perceived smooth, flat surfaces as water, even when other sensory information contradicted that interpretation.2PubMed Central. Innate recognition of water bodies in echolocating bats This is an innate response, not a learned one. A still swimming pool returns the same kind of echo as a natural pond, so a bat approaching it for a drink has no acoustic reason to treat it differently. The problem comes after contact: a concrete pool offers no branch, no muddy bank, no vegetation to grip. The bat is stuck.
Beyond drinking, many bat species forage directly over water. Insects concentrate near the surface of ponds, rivers, and lakes, making these prime hunting grounds. Daubenton’s bat, a European species particularly well known for water-surface foraging, flies just centimeters above calm water, directing its echolocation beam parallel to the surface to detect insects sitting on or just above the waterline.3Functional Ecology. Echolocation constraints of Daubenton’s Bat foraging over water Flying that low means any disruption to the flight path risks putting the bat in the water.
How Echolocation Shapes the Bat-Water Relationship
Water surfaces create both opportunities and problems for echolocating bats. A smooth, calm surface acts like a mirror for ultrasound: the echolocation pulse hits the water and bounces away at the same angle it arrived, producing a clean, predictable return. This mirror-like quality is what allows bats to identify water bodies so reliably. It is also what makes foraging over water attractive, because an insect sitting on a perfectly smooth surface stands out acoustically the way a pebble on a polished table stands out visually.
Rippled or turbulent water is a different story. When the surface is disturbed, each wavelet scatters the echolocation pulse in multiple directions, creating a noisy mess of echoes that can mask the faint return from a small insect. Studies of Daubenton’s bat found that at even modest angles of approach, rippled water produced significantly more acoustic clutter than smooth water. The ripples also generated their own ultrasonic noise in the form of short pulses, averaging about six per second, that could interfere with the bat’s ability to detect prey echoes.3Functional Ecology. Echolocation constraints of Daubenton’s Bat foraging over water The bat was essentially operating at the very edge of what its sonar could handle, detecting prey echoes that were roughly the same intensity as the background clutter.
This is why bats that forage over water strongly prefer calm conditions. Windy nights, rapids, ocean surf: these are not bat habitat. The species most associated with water-surface foraging are found over slow rivers, sheltered lakes, and protected pools. The acoustic physics of echolocation essentially restrict water-foraging bats to the quietest water available.
Why Evolution Did Not Build a Swimming Bat
Given that bats have been around for more than 50 million years and have diversified into over 1,400 species, filling ecological roles from insect control to pollination to fruit dispersal, you might expect that at least one lineage would have evolved into a competent swimmer. Plenty of birds manage it: puffins and auks fly underwater, ducks paddle on the surface, and penguins abandoned flight for swimming entirely. Yet no bat has made a comparable transition. The reason lies in a fundamental constraint built into the bat body plan.
A bat’s wing is not just a modified arm. It is a membrane that stretches from the elongated finger bones all the way to the hindlimbs and, in most species, to the tail. This means the forelimbs and hindlimbs are physically connected by a sheet of skin. Research examining limb proportions across the bat family tree has demonstrated that this membrane enforces strong evolutionary integration between the forelimb and hindlimb: changes to one part of the skeleton tend to be coupled with changes to other parts.4PubMed. Evolutionary integration of forelimb and hindlimb proportions within the bat wing membrane inhibits ecological adaptation In birds, the wings and legs are independent structures that can evolve in different directions. A penguin can have stubby, rigid flippers for swimming while retaining strong, upright legs for walking. A bat cannot easily decouple its limbs this way.
The result is that bats show much lower rates of body-shape diversification than birds do. Different bat species vary in the proportions of their wing bones and the shape of their thumb and hindlimb, accommodating differences in flight style and roosting habits. But the overall body architecture stays remarkably similar across the entire order. The wing membrane, the very structure that made bat flight possible, also locks the skeleton into a relatively narrow range of forms.4PubMed. Evolutionary integration of forelimb and hindlimb proportions within the bat wing membrane inhibits ecological adaptation Powered flight enabled by a membranous wing is both the bat’s greatest innovation and its defining limitation.
A comparison with pterosaurs, the other group of vertebrates that flew on skin membranes, reinforces the point. Some large pterosaurs are thought to have been fish-eaters, which has led to speculation about whether any of them swam. But as one analysis noted, no known pterosaur shows a body form resembling the wing-swimming birds like auks. The authors pointed out that if any membrane-winged flier could swim with its bat-like legs, you would expect some bats to do it too, and they do not.5Academic Press / ScienceDirect. The Membrane Wings of Bats and Pterosaurs The membrane wing design, whether in a pterosaur or a bat, appears to be fundamentally incompatible with any serious aquatic lifestyle.
The Problem of Getting Out
For a bat, the real danger of water is not swimming through it but launching from it. Most bats cannot take off from a flat surface the way a bird can. Their hindlimbs are weak compared to those of similarly sized birds, and many species initiate flight by dropping from a perch, using gravity to gain the airspeed needed to start generating lift. A bat sitting on the surface of a pond does not have that option. It needs to somehow generate enough upward force from a dead stop, while waterlogged, to become airborne.
Some bats manage this better than others. Species that roost in exposed locations or frequently land on flat surfaces tend to have relatively stronger jumping ability from the ground. But even for these species, a water surface is worse than solid ground: the surface gives way under the push, absorbing energy that would otherwise launch the bat upward. The wing membranes, once wet, are heavier and less aerodynamic. And every failed takeoff attempt costs energy the bat may not have to spare.
This is why the edge conditions matter so much. A bat that lands in a natural stream or pond can usually paddle to shore and grab onto vegetation, bark, or rock. From an elevated perch, even a few centimeters above the water, it can drop and fly. A bat that lands in a swimming pool with smooth tile walls and a wide, featureless surface has no such option. Wildlife rehabilitators report that swimming pools are one of the most common water-related hazards for bats in suburban areas. Floating a small board or a piece of towel over the edge of a pool can give a stranded bat something to climb onto.
Bats That Live Near Water
Even though no bat is a swimmer, many species are strongly associated with aquatic habitats. Daubenton’s bat in Europe, the water myotis in North America, and various species of fishing bats in the tropics all depend on water for foraging. Fishing bats are the most dramatic example: species in the genera Noctilio and Myotis vivesi use their enlarged hindlimb claws to gaff small fish and crustaceans from the water surface. These bats fly low, detect prey by echolocation or by the ripples prey create, and rake their feet through the surface in a quick pass. They do not enter the water bodily. The entire interaction is aerial: the bat swoops, the claws break the surface for a fraction of a second, and the bat climbs away with or without a catch.
The greater bulldog bat (Noctilio leporinus) is perhaps the most specialized. Its feet and claws are proportionally enormous, and its legs are long relative to other bats, giving it the reach to snag fish while keeping its body and wings clear of the water. Even this species, arguably the most aquatic bat alive, does not swim. Its body plan is still locked into the same membrane-constrained architecture as every other bat. It has simply pushed the limits of what you can do with that architecture while staying airborne.
What to Do If You Find a Bat in Water
If you find a bat struggling in a pool, birdbath, or water trough, the priority is giving it a way out rather than grabbing it directly. Bats can carry rabies, and a stressed, waterlogged bat is more likely to bite. Slide a towel, a piece of cardboard, or a thin board under the bat so it can climb on. Move the object to a sheltered, elevated spot nearby, like a tree branch or a fence post, where the bat can dry off and take flight on its own. Most bats that are rescued from water and given a dry perch will fly away within an hour once they warm up and their wing membranes dry.
If the bat does not fly away after several hours, appears injured, or is found during daylight, contact a local wildlife rehabilitator. Do not attempt to feed it or give it water directly. Bat metabolism is fast and their body temperature can drop quickly when wet, so time matters. In areas where swimming pools are common and bats are active, a simple ramp or float left at the pool edge overnight can prevent these incidents entirely. Commercial “critter escape ramps” designed for pools work for bats as well as for frogs and rodents.
How Bat Swimming Became an Internet Fascination
Videos of bats swimming have gone viral multiple times over the past decade, and for good reason: the sight is genuinely bizarre. The animals look both determined and completely out of their element, churning across the surface with wings that are clearly designed to push air, not water. The footage has also sparked persistent misconceptions. Some viewers assume the bat is hunting or playing. In reality, virtually every video of a swimming bat shows an animal in distress, trying to reach an edge it can climb. The frantic wing-paddling is not a sign of competence; it is the bat’s only option.
Another common misconception is that certain bat species are “aquatic” or “semiaquatic.” No living bat species fits either description. The fishing bats discussed above are sometimes described this way in casual sources, but their relationship to water is analogous to an osprey’s: they hunt over it and grab prey from it, but they live in the air. The distinction matters because calling a bat aquatic implies adaptations for moving through water that simply do not exist in the order Chiroptera. Every bat, from a two-gram bumblebee bat to a fruit bat with a one-and-a-half-meter wingspan, is an obligate flier that tolerates water contact only briefly and reluctantly.