Maritime Coordination · RGB
Smart Buoys: Relays Between Sky and Sea
Floating sensors and power sources that watch, measure and protect the sea.
Maritime Coordination RGB
GPS is one of the quiet miracles of modern life, and it stops at the waterline. The radio signals it depends on cannot travel through seawater, so the moment a diver, a submersible or a sensor slips beneath the surface, it loses its place in the world.
Sound is different. The ocean carries it farther and faster than almost anything else. Our smart buoys are relays that stand with one foot in each world: they take their position from the satellites above and pass it down into the water as sound. Linked together, they become a positioning grid for everything below, and at the same time an instrument that can map the ocean itself.
They are designed to need nothing from us once they are in the water. They power themselves from sunlight, waves and moving water, and they hold their places without a single tether, by finding each other.
- Speed of sound in seawater
- About 1,500 m per second, four to five times faster than in air
- GPS signal underwater
- None. Radio does not penetrate seawater
- Range of low-frequency sound
- Up to thousands of kilometres
- Power source
- Sun, waves and current
- Tethers
- None. The buoys find each other
The idea
One foot in each world
Each buoy carries a satellite receiver and precise clock above the water, and an acoustic transducer below it. Because every buoy knows exactly where it is and exactly what time it is, any sound that passes between buoys, or between a buoy and something beneath it, becomes a measurement. Timing the journey of a sound tells you a distance. Many such journeys, crossing in every direction, tell you a great deal more.
Two jobs, one network
A grid and a scanner
The GPS-style grid
On land, your phone finds itself by timing signals from several satellites. Underwater, the buoys play the satellites' role. A diver, robot or seafloor marker sends or answers a short acoustic ping, each buoy times its arrival, and the position falls out of the geometry, usually from four or more buoys at once. Systems built on this principle, known as GPS intelligent buoys, have been tracking submersibles since the 1990s, and portable versions can be set up in under an hour. Pointed at fixed markers on the seabed, the same technique, called GNSS-acoustic geodesy, measures how the seafloor itself moves, to within centimetres.
Tomographic mapping
A hospital CT scanner builds a picture of the inside of the body from many X-ray paths crossing at different angles. Ocean acoustic tomography, proposed by oceanographers Walter Munk and Carl Wunsch in the late 1970s, does the same with sound. Because sound speed in seawater depends mostly on temperature, the travel time between two known points is really a measurement of the water between them. Send sound both ways and the difference reveals the current. With enough crossing paths, a mathematical inversion turns travel times into a three-dimensional map of heat and flow beneath the surface.
Here is the design insight at the heart of our smart buoys. In any underwater positioning system, the largest source of error is not knowing exactly how fast sound is travelling through the water at that moment. And the speed of sound through the water is precisely what tomography measures. So rather than treating positioning and mapping as two separate products, we treat them as two halves of one loop: the tomographic map corrects the grid in real time, and every ping the grid makes adds another path to the map. The more the network is used, the sharper both become.
Beyond sound
Flux and polarity
Sound is the only signal that carries far underwater, but it is not the only one that gets through. Magnetic and electric fields pass through seawater where radio cannot, and reading them asks nothing of the ocean but attention. Our buoys add a second, silent sense alongside their acoustic one.
Magnetic anomaly mapping
A magnetometer on each buoy reads the tiny local variations in Earth's magnetic field created by the rock below. Seafloor basalt records the planet's past polarity reversals as alternating magnetic stripes, the same stripes that helped prove plate tectonics, so the grid becomes a slow, patient geologist for our tectonic stabilization work. Once an area's magnetic signature is mapped, a vehicle can find itself by matching what it senses against the map, with no transmitter at all.
Current by induction
Seawater is a conductor, and when it flows through Earth's magnetic field it generates a small voltage. Measure that voltage across a known distance and you measure the water moving between those points. Retired undersea cables have been used this way for decades to track major ocean currents. Electrodes on neighbouring buoys can do the same across a corridor, continuously and in complete silence.
Magneto-inductive positioning
Low-frequency magnetic fields can locate a diver or robot over tens of metres, untroubled by bubbles, echoes or murky water. Where acoustics struggle, around a habitat, a wreck or a reef, this fills the gap.
Each sense has its limits. Magnetic signals fade quickly with distance, so they work close in or as a coarse layer, while sound remains the precision backbone. A buoy's own steel and electronics distort readings, so the magnetometer hangs below on a non-magnetic line. And geomagnetic storms shift the field everywhere at once, so the network keeps a reference to subtract them out. Together, the three layers check one another: sound for precision and 3D mapping, magnetics for passive navigation and geology, induction for silent current monitoring.
Self-sufficient by design
Powered by what surrounds it
A buoy that needs a boat to change its batteries is a buoy that will eventually be abandoned. Ours are built in layers, each harvesting a different part of the environment, so that monitoring never depends on a visit from shore.
- Layer 1: Solar skinThe upper surface is covered in lead-free perovskite cells. Perovskites are light, efficient and can be printed onto curved surfaces, but their known weakness is moisture, heat and ultraviolet light, all of which the open ocean has in abundance. We are engineering their composition and encapsulation specifically for life at sea, and durability is the question our testing has to answer honestly.
- Layer 2: Dual-band mirrorBeneath the skin, the same idea as our Dual-Band Solar Harvester: dichroic films pass the wavelengths solar cells use best and reflect the infrared, which a parabolic shape focuses into a small thermal store. One surface becomes both a panel and a mirror, and the stored heat keeps electronics and batteries in their comfortable range through cold nights.
- Layer 3: Wave generatorInside the hull sits our compact wave energy converter, small enough to fit within the buoy itself. Every rise and fall of the sea becomes charge, day or night, sun or storm.
- Layer 4: Flowing waterCurrent moving past the hull is one more source to draw on. The same motion that carries the buoy along keeps its listening and sensing powered.
- Layer 5: Energy budgetPower decides behaviour. Listening and passive sensing run continuously on a trickle. Transmitting and moving draw from storage. When reserves run low, a buoy goes quiet and drifts, rejoining the grid once it has recharged, rather than failing.
The layers also help each other. Because every buoy can steer itself, it can turn its mirror toward the sun, and because it can sense the water around it, it can choose where to sit to catch the best waves.
- Moorings
- None
- Lines in the water to tangle wildlife
- None
- How a buoy keeps its place
- It homes in on its neighbours
- Grid shape
- Changes with the job
- Every encounter
- A unique signal
No tethers
A moving chessboard
Most ocean buoys are anchored to the seabed by long lines, and those lines are among the sea's quiet hazards for whales and turtles. Ours have none. Instead, each buoy keeps its place the way a robot vacuum finds its way home to its dock: it homes in on a beacon. Here the beacons are its neighbours. Every buoy listens for the pings and signatures of the others and steers to hold its position in the formation, so the grid holds itself together.
This is not wishful thinking. Wave-propelled autonomous surface vehicles already hold station and travel for months at a time without moorings, driven by the same wave motion our buoys harvest.
Untethered, the grid becomes a moving chessboard. Pieces can tighten around a survey site, spread wide to map open water, form a line along a migration route, step aside to clear a path for whales, or regroup after a storm. A moving grid even makes for a better map: oceanographers have already run tomography with moving ships as part of the array, because every new position adds new crossing paths.
When pieces meet
Every encounter leaves a fingerprint
When two buoys close in on each other, their signals overlap and interfere. The pattern that results depends on their exact distance and angle and on the water between them, so no two encounters ever produce the same one. Rather than treating that interference as noise, the network uses it.
A handshake
The interference pattern acts as a signature only those two buoys, in that place, at that moment, could produce. It confirms who met whom.
A tune-up
Two buoys close together, at a distance both can measure, are the perfect moment to check clocks, compasses and sound speed against each other.
A sample
Because the pattern depends on the water between them, every meeting is also a measurement, logged as one more point on the map.
A soft touch
Encounters are meant to be close, not crashes. Soft fenders and approach limits keep pieces from damaging each other or anything nearby.
Inside a smart buoy
What each relay carries
Every buoy is a node. Alone it is a weather station and a listening post; in a group it becomes infrastructure. Today's ocean-observing buoys already show how much a single node can do, and our design builds on them.
Satellite receiver and clock
Precise position and precise time. Every other measurement depends on these two numbers being right.
Acoustic transducer
Sends and receives the pings and coded signals that carry position, time and data through the water.
Listening hydrophone
Passive ears that hear whales, ships and storms. Listening comes first; transmitting comes second.
Magnetometer and electrodes
The silent senses: magnetic anomalies for navigation and geology, induced voltages for current.
Environmental sensors
Temperature, salinity, pressure and wave motion at the buoy, to anchor and check the tomographic map.
Layered harvesting
Perovskite skin, dual-band mirror, wave generator and flow, managed by an energy budget that never lets it fail hard.
Homing and station-keeping
Quiet, wave-assisted propulsion and the logic to find its neighbours, hold formation and reshape the board.
Relay uplink
Buoys talk to each other by radio and to shore by satellite, passing data along the chain so no single node has to reach land.
What the grid makes possible
Uses across all three arms
Whale-safe waters
Listening buoys are already proving themselves. Off California, the Whale Safe system uses a hydrophone buoy that automatically recognises blue, humpback and fin whale calls and relays detections by satellite, so ships know when to slow down. A smart buoy grid could carry that kind of early warning along entire migration corridors, and move with the whales.
Watching the seafloor move
Subduction zones like Cascadia build up strain offshore, where land-based GPS can't see it. GNSS-acoustic measurements from autonomous surface platforms are beginning to fill that gap, and magnetic mapping adds the geology beneath. This is the sensing layer behind our tectonic stabilization work.
Heat beneath the surface
Satellites see the skin of the ocean. Tomography sees inside it, averaging over long distances to track how heat and currents change through the water column, season by season.
Navigation for sea habitats
Divers, maintenance robots and rescue teams working around a Pacific habitat need to know where they are. A standing grid gives them a map with coordinates, not guesswork.
Tracking living structures
Floating mangrove platforms, rig reefs and Biorock sites can be positioned, monitored and checked against their baseline, so we know whether they are helping.
Search and recovery
Portable buoy grids are already used to locate flight recorders and distressed submarines. A self-powered grid that can move itself to the search area shortens the wait from days to hours.
Quiet engineering
A network that listens before it speaks
Anything that puts sound or energy into the sea has to answer to the animals that live by it. When basin-scale acoustic thermometry was tested in the 1990s, concern over its effects on marine mammals led to dedicated research programs, and we take that history seriously. Our smart buoys follow the safe disciplines of Pacific Habitation, with rules of their own:
- Listen first. Every buoy runs passive detection, and transmissions pause when nearby whales or dolphins are heard.
- Use the quietest signal that does the job, and only as often as the job needs.
- Choose frequencies and timing to avoid the calls of local species and their breeding and migration seasons.
- Prefer passive fields. Reading magnetic and electric signals emits nothing; any active electromagnetic signal follows the same listen-first rules, mindful of sharks and rays that sense electric fields and the many animals that navigate by Earth's magnetism.
- Move slowly and quietly. Station-keeping uses gentle, wave-assisted propulsion, never high-speed thrusters.
- Measure our own noise in the water, publish it, and change the design if the numbers say so.
- Let one signal do several jobs wherever possible, so the network adds as little to the sea as it can.
Status
Where we are
Smart buoys are in the concept stage. Every step is something that can be built, tested and measured before the next one begins.
Self-powered relay
One buoy holding a satellite fix, passing time and position into the water, and running on its own harvested power.
Finding each other
Two untethered buoys homing on one another and holding formation, recording the interference signature of every encounter.
Sheltered-water grid
Four buoys in calm, shallow water, locating a diver or small robot by sound and magnetics and checking accuracy against known points.
First map
Reciprocal sound paths and induced currents turned into a live picture of temperature and flow, then fed back to sharpen the grid.
The moving chessboard
An open-water grid that reshapes itself along a route that matters, with whale detection and public data from the first day.
Keep exploring
Related work
Further reading
- Underwater GPS (Discovery of Sound in the Sea, University of Rhode Island)
- Ocean acoustic tomography (overview)
- Munk, Worcester and Wunsch, Ocean Acoustic Tomography (Cambridge University Press)
- Shallow water seafloor geodesy with Wave Glider-based GNSS-acoustic surveying (Earth and Space Science, 2023)
- Whale Safe (Benioff Ocean Science Laboratory, UC Santa Barbara)