Why a bird that can swim and fly matters
A flying machine has a bad time the moment it meets water. Air and water may both count as fluids, but they don’t behave like distant cousins. Water’s hundreds of times denser than air, which means a drone that slips neatly through the sky can suddenly feel like it’s flown straight into a wall. Motors strain, and wings drag. Control gets messy fast. A machine designed for one medium usually pays for that design choice in the other.
Birds have already figured out a version of this problem. Puffins dive into the sea, chase prey underwater, then pop back into the air without calling a tow truck. Gulls manage a less theatrical version of the same trick, skimming, landing and taking off from surfaces that’d make most aircraft sulk. Their bodies are built for a lot of compromise, and nature seems to have been fine with that arrangement for a long time.
The real trick isn’t flying or swimming on their own. It’s moving between the two without turning the machine into a clumsy guest in either world.
That handoff is exactly what engineers at MIT and EPFL in Lausanne set out to tackle. Instead of building another standard drone and hoping it could survive a splash, they made a hybrid flyer-swimmer, a machine meant to work in both air and water. The idea sounds almost cheeky at first, like somebody asked, “What if a robot tried to be a puffin?” But the engineering problem underneath it is very real. A vehicle that can cross that boundary cleanly could reach places that are awkward for boats and annoying for aircraft, then come back with data instead of a story about how it nearly got lost at sea.
Those places aren’t hard to imagine. Think of rocky coastal pockets where a boat would have to slow down, anchor and fight the terrain. Storm-damaged shorelines, or isolated patches of water where a plane can pass overhead but not touch down, think of ice edges, shallow bays. Think of the sort of marine sampling mission that sounds simple in a meeting and turns into a logistics headache once weather, distance and fuel costs join the conversation. A hybrid machine can cut across some of that friction. It can fly to the site, enter the water and move in the same place where the measurements need to be taken.
That’s a different job from what most drones do. Conventional quadcopters and fixed-wing aircraft are built around air only. Boats are built around water only. A craft that can work in both mediums sits in a narrow, awkward middle ground, which is probably why the concept’s taken so long to get beyond sketches and lab tests. The physics refuse to be polite. Control surfaces that work well in air may become useless underwater. Shapes that slice water efficiently may struggle to generate enough lift overhead. Even the act of switching from one to the other is a problem that has to be solved rather than wished away.
So the appeal here isn’t novelty for novelty’s sake. It’s access. Oceanographers, marine biologists and coastal teams often need repeated measurements from spots that are difficult to reach with a person on board or a conventional aircraft overhead. A machine that can land, dip, sample and launch again could reduce the cost and risk of those trips. It also could make short, frequent missions practical, which matters when conditions change by the hour instead of by the season.
That’s the promise sitting behind the very odd, very charming idea of a robo-puffin. The next question’s how the machine’s built so it can actually pull off the switch without flopping, sinking, or performing an expensive one-way splash.
Inside the FAAV: a birdlike machine with a waterproof core
Calling the machine a drone would be a bit too loose. Its builders use a more exact label: a flapping-wing aerial-aquatic vehicle, or FAAV if you don’t feel like wrestling with the full phrase before lunch. That name fits because the robot’s built around a birdlike body plan rather than the usual quadcopter setup. It’s a compact central fuselage, two flexible wings and a tail that can be shifted to change how it moves through air or water.
The whole thing’s tiny by vehicle standards, coming in at well under a pound. That matters because weight is a constant headache for any machine that has to leave the surface, fly, then touch water without turning into a soggy brick. A heavier body would need more lift, which means more motor, more battery and more structure, which then adds even more weight. The FAAV tries to avoid that trap by staying lean and simple.
The clever part isn’t that the robot can do two jobs. It’s that the same body is built to survive both jobs without getting torn apart by the switch.
Inside the fuselage sits a waterproof electric motor and a battery sealed away from the water. They don’t spin propellers in the usual drone style. Instead, the motor turns a crankshaft, and that shaft drives the wings in a fixed rhythm. It’s a mechanical setup with more in common with a living wingbeat than with the whine of a hobby drone. That choice does a lot of the work here. A flapping mechanism can change how the wings meet the air or the water in ways a rigid propeller can’t, especially when the craft has to move through both media in quick succession.
The wings themselves are more interesting than they first appear. They’re not hard panels, and they’re not ordinary fabric stretched over a frame. They use thin membranes treated with water-repelling particles, so droplets don’t cling to them and add drag. That’s a small detail with outsized consequences. Water sticking to a wing can make the robot heavier, blur its motion and slow the transition between mediums. A membrane that sheds water more readily’s better suited to a flying underwater robot that has to crawl through liquid one moment and push through air the next.
This is where the FAAV starts to look less like a lab toy and more like a biomimetic robot that borrowed a few sensible tricks from seabirds. The wings flex rather than snap rigidly in place, which gives the machine some give when it meets resistance. In water, that flexibility helps keep drag down. In air, the same wings can still generate enough lift to carry the body clear of the surface. It’s a compromise, of course. Every hybrid design is. A machine improved only for flight would likely fail underwater. What was improved by a machine is only for swimming would struggle to get airborne. The FAAV sits in the awkward middle on purpose.
The tail plays a quieter role, but it isn’t decoration. Its angle can change, which lets the robot tip its body for different phases of movement. Point it one way and the machine can pitch upward to climb into the air. Angle it another and the body can tilt downward for entry into the water. That steering surface gives the robot a way to manage its posture without relying on some bulky appendage or external launcher. In plain terms, it helps the craft decide whether to nose up, nose down, or hold steady while the wings do the heavy lifting.
That kind of control also makes the design feel more like a bird than a conventional flying machine. The robot doesn’t depend on spinning rotors perched above a frame. It depends on coordinated motion across the fuselage, wings and tail, with each part doing one job that feeds the next. The result’s compact, sealed and oddly elegant for something with a battery pack and a crankshaft inside.
The design choices here point to a very specific goal. This isn’t a machine meant to skim over a lake for a few seconds and call it a day. It’s built to cross a boundary most vehicles avoid altogether. You can see why the project’s drawn interest from people who follow tech news and lifestyle tech with one eyebrow raised. It feels futuristic, sure, but the engineering’s stubbornly practical.
A robotic puffin doesn’t need feathers to act birdlike. It needs a body that won’t flood, wings that can survive repeated immersion and a tail that can steer the whole arrangement without overcomplicating it. That’s the trick the FAAV’s trying to pull off, and the next test is the hardest one of all: whether all those neat parts still work when the machine leaves the tank and tries the real thing.
How the robot pulled off the water-to-air handoff
Once the robot had a waterproof core and flapping wings, the real test began: could it leave the water cleanly and keep enough control to keep flying? That question sounds simple until you remember that water’s far denser than air. A body that moves gracefully in one medium can turn sluggish, unstable, or just plain awkward in the other. The team behind the MIT robot and EPFL robot didn’t settle for a neat lab demo, either. They ran trials in a tank first, then took the machine out to Lake Geneva to see how it behaved when the water surface stopped acting like a polite classroom prop.
The hard part isn’t flying or swimming. It’s surviving the handoff between the two without losing control.
That handoff depended on a handful of tunable variables. The researchers changed wing size, flapping rate and tail angle to see which combinations let the vehicle move from one medium to the other without stalling halfway through the process. Some settings made the machine glide through water more smoothly but left it weak in the air. Others helped it generate lift after takeoff, yet created too much resistance below the surface. The robot didn’t have the luxury of choosing one perfect compromise. It had to act like an aquatic drone one second and a flyer the next, which is the sort of assignment nature assigns to birds and then leaves engineers to figure out with tools and spreadsheets.
Wing size turned out to matter more than you might expect. The medium-sized wings performed best. Smaller wings were too limited in the water and didn’t push enough air once the robot emerged. Larger wings created more drag in the tank and made the transition messier. The middle ground worked because the wings had enough flex to cut through water without folding into uselessness, but they stayed stiff enough to keep producing lift in air. That balance sounds almost annoyingly sensible, but it took real testing to land on it.
The robot’s movement also looked uncannily birdlike. Its speeds and wingbeat rates landed near the range used by real birds, which is the sort of detail that matters if the goal is a machine that can borrow biology’s tricks without copying it wholesale. The robot wasn’t flapping randomly or relying on brute force. Through two very different fluids. It used a rhythm that fit the physics of a small body moving. That timing helped the machine maintain momentum as it rose from the surface and shifted into flight.
Body angle mattered too. The most successful takeoffs happened when the robot pitched itself steeply upward, at about seventy degrees. That angle gave it enough upward drive to break free of the water instead of skimming along the surface like a badly behaved toy. Too shallow, and it hesitated. Too steep, and it risked wasting energy or losing stability. Seventy degrees turned out to be the sweet spot for the transition. A tidy little piece of geometry, really, even if the robot probably didn’t appreciate being told to mind its posture.
The surface launch’s where the machine differs from many diving birds. Puffins and other seabirds often use their feet to help spring themselves out of the water. This robot didn’t need that extra push. It got airborne from the water alone, using the wing motion, body angle and tail control built into the design. That makes the result more than a clever imitation of a bird. It means the machine can handle a launch sequence without legs, which is handy because the whole contraption has already had enough mechanical drama for one prototype.
The EPFL overview of the flapping robot describes the same basic test program in water and air, but the larger point here is practical rather than theatrical. The team wanted a machine that could move between a lake surface and the sky without requiring a crane, a runway, or a minor act of engineering theater. So far, the numbers suggest they’ve gotten much closer than a standard drone would on its own.
That is where the lab work becomes interesting. A robot that can launch from water without feet, with a body angle that has already been tuned in tests, is not just a stunt. It gives the engineers a way to think about repeated takeoffs, not one-off novelty jumps. And once a machine can do that reliably, the conversation shifts fast from “can it work?” to “where does it go next?”
What ocean scientists could do with it next
The first clean trip from water to air gets the attention. The harder work comes after that: making the machine behave when the sea is messy, the wind’s rude and nobody has the patience for a perfect lab day.
That’s where the next round of testing comes in. The team wants to improve wings that can both flap and turn, since the current setup gets the robot off the water but still leaves plenty of room for better steering. Right now, the puffin-shaped machine can make a dramatic little exit from the surface. In the field, though, a field tool needs more than a dramatic exit. It needs to hold a line, change course without fuss and cope when the air isn’t cooperating. If the wings can handle those demands, the robot becomes less of a curiosity and more of a working vehicle.
A machine that can leave the water, cross a short stretch of air, and come back again could spare researchers a lot of expensive back-and-forth.
The next tests will push it into rougher conditions, including choppy water and windy air. That sounds obvious, but obvious conditions are often the ones that break a prototype. A calm tank and a windless lake tell only part of the story. Out on the coast, the surface can slap against the hull, gusts can shove a light aircraft sideways, and a clean takeoff can turn into a clumsy splash in a hurry. A vehicle that works only when nature is being polite isn’t much use to anyone who actually studies the sea.
That matters for a fairly practical list of users. Oceanographers could send it to places where a boat’s too slow, too costly, or too risky to deploy every time they want a reading. Marine biologists might use it near whale groups, where a small airborne craft could get close enough to record surface conditions, take measurements, or spot animal movement without dragging a crewed vessel through the scene. Coastal communities could also have a use for something like this, especially if they need frequent checks on changing conditions near shore, ports, or sea ice and don’t want to launch a full expedition every time.
The robot’s appeal comes from that combination of flight and water access. A normal drone can’t sample below the surface. It can’t hop over a breakwater, a stretch of kelp, or a patch of ice to reach the next spot. This machine tries to do both, which gives it a narrow but useful job description. It could fly near ice edges, drop into the water to collect a sample or take a reading, then lift off again and head to another point without a human ferrying it there by boat.
Ports are another obvious target. They’re busy, noisy and full of obstacles, which makes them awkward for repeated sampling by hand. A small aerial-aquatic robot could move around a harbor margin, check water conditions and return with data before a crew’s even finished warming up the coffee. That probably sounds a little smug, but the advantage’s real. Repeating the same measurement several times in a day is often the difference between a useful data set and a guess stitched together from one lucky snapshot.
The longer-term promise isn’t a flashy one. It’s cheaper, repeatable ocean data collection. Not once a week, When the weather forecast looks friendly, but often enough to catch changes as they happen. If the machine can survive rough water, shift direction cleanly and keep its balance in wind, it could become a routine tool rather than a one-off demonstration. That’s the part scientists usually want anyway, even if the robot looks like it escaped from a very specific museum gift shop.
