Can a Robot Fly Out of the Water on Wings Alone? Swim-and-Fly Robots Explained

A puffin flies through the air, then dives in and flies underwater with the same wings. Researchers at MIT, EPFL and Northwest Indian College built a 250-gram robot to test what that takes: no propeller, no legs, just two flexible flapping wings.

In a lake in Switzerland, starting on a stand 20 cm under the surface, it flapped its way out and flew. At a 70° angle, it made it out four times out of four.

In this independent explainer, I walk through how it works and what the paper shows.

In this video

• Why water, about a thousand times denser than air, is so hard on a wing, and how diving birds cope
• The robot: a slim body, a tail and fabric wings almost 90 cm across, with its own battery and one motor driving both wings
• Flexible wings instead of folding ones: they bend back underwater, so the motor can reach 6 flaps a second. The team calculates rigid wings would hold it under 1 flap a second
• Wing size: small wings swam fastest, almost 1 m/s, but couldn't make enough thrust for take-off. Each meter cost about the same energy whatever the size. The medium wings were the compromise: they could fly and still swam at nearly 0.8 m/s
• The tail: with none, the robot can't stay stable in the air. A long one drags it back in. A short tail right behind the body worked
• The lake: out in about a second, in 8–10 strokes, and why too shallow an angle fails and too steep a one can tip it over backward
• Energy: leaving the water takes about 190 W/kg, more than ten times the power of slow swimming, and only about 1/40 of the energy ends up as speed and height. By the team's calculation, for trips beyond about 15.5 m, getting out, flying and diving back in costs less than swimming slowly the whole way
• Plunge diving: in at 5 m/s, slowed to 0.5 m/s, about 60 g on impact
• What it says about birds, and what it didn't show: fresh water only, flapping set ahead of time, lake exits from a stand at a hand-set angle, and no single run of the whole swim, leap, fly and dive cycle

For engineers

One brushless motor drives both wings through a 23:1 planetary gearbox and a 2:1 crank linkage, at 60° amplitude, from 0.1–6 Hz in water to 5.2–11 Hz in air. The wings are a nylon membrane on a carbon skeleton with a 3 mm leading-edge spar; five stiffness levels (spars of 2.0–4.5 mm) and three sizes (430 mm semi-span ± 100 mm, same aspect ratio). The robot is neutrally buoyant, and waterproofing added 13 g (5.2%).

Wind-tunnel tests ran at 6 m/s and 20° angle of attack; swimming speed at 5 Hz was 0.95, 0.79 and 0.64 m/s for small, medium and large wings. Power: 18 W/kg swimming at 1 Hz, 74 W/kg in cruising flight, 190 W/kg for egress. Lake exits ran on a timer at 10 Hz for 5 s; Fig. 3B analyzes 11 of them from 50° to 85°.

The paper

"Leaping out of the water: Aerial-aquatic locomotion with flapping wings"
Raphael Zufferey, Simon L. Jeger, Moritz Hüsser, Fernando Ruiz, Anthony Lapsansky, Auke Ijspeert, Dario Floreano
AURA Lab, Massachusetts Institute of Technology; Laboratory of Intelligent Systems and Biorobotics Laboratory, EPFL, Lausanne; Salish Sea Research Center, Northwest Indian College
Science 393(6807), 207–211, 9 July 2026, doi:10.1126/science.aeb6744

Read the paper (Science)
Free author manuscript with the supplementary materials
Data and robot design files

Supported by the MSCA Fellowship H2020 under grant 101029670.

The paper goes much deeper: the torque analysis behind the flexible wings, the wind-tunnel and pool data, the tail and stiffness trials, and six movies. If you work on bio-inspired or aerial-aquatic robots, it's worth reading in full.

This is an independent explainer. I'm not affiliated with or endorsed by the authors, MIT, EPFL or Northwest Indian College, and the research is all theirs. The animations are my own illustrations of what the paper describes, not footage from the experiments, and the board sketches are mine too. Charts marked schematic are sketches; the rest follow the paper's numbers, with some values read off its figures. Any mistakes in the explanation are mine.

I'm Bora Celik from Piccard. I explain new research in ocean science and robotics.