The Sixth Sense: How Great White Sharks Can Feel Your Heartbeat Through the Water

1 July 2026 | White Shark Ocean

Imagine being able to sense the heartbeat of an animal buried under sand. Not hear it, not feel the vibration — but detect the minute electrical field produced by the contraction of its heart muscle, from a distance, through water and sediment, with enough precision to locate it exactly. This is not a hypothetical superpower. It is something great white sharks do routinely, using a sensory system so sensitive that it detects electrical fields measured in billionths of a volt.

Humans have five senses. Great white sharks have at least seven, possibly eight. The one that most people have never heard of — electroreception — may be the most remarkable of all.

What the Ampullae of Lorenzini Are

Look closely at a great white shark's snout and you will see something that resembles a scattering of dark pores across the skin. These are the openings of the ampullae of Lorenzini — a network of jelly-filled canals named after the Italian physician Stefano Lorenzini, who first described them in 1678. He did not know what they were for. It took nearly three more centuries before science understood their function.

Each ampulla is a small, fluid-filled sac connected to the skin surface by a thin tube packed with a highly conductive gel. Specialised sensory hair cells line the ampulla walls, and these cells respond to differences in electrical potential between the pore opening at the skin surface and the interior of the ampulla. When an electrical field passes through the water, it creates a tiny voltage difference across the length of the canal — and that difference is detected, measured, and relayed directly to the brain.

In great white sharks, these structures are concentrated in clusters across the snout and lower jaw: paired clusters above the eyes, V-shaped clusters around the nostrils, elongated clusters beneath the snout, and a distribution along the chin. The arrangement is not random. It forms a three-dimensional electrical field map that allows the shark to triangulate the position of a source with considerable precision.

How Sensitive They Are

The ampullae of Lorenzini are tuned to detect low-frequency electrical signals in the range of 1 to 8 hertz. This is not coincidental: the electrical signals produced by the muscle contractions of fish, the nerve impulses of invertebrates, and the metabolic activity of living tissue all fall within this frequency range. Every animal in the ocean is producing electrical signals continuously. The great white's electroreceptive system is calibrated to detect them.

The sensitivity is extraordinary. Research has shown that the ampullae can detect electrical fields as weak as five billionths of a volt per centimetre. To put this in context: this is comparable to detecting the electrical potential produced by a standard AA battery connected to electrodes placed more than 1,600 kilometres apart. A fish buried under sand, with its heart beating and its gills moving, produces an electrical field well within this detection range. The great white does not need to see it, smell it, or hear it. It can feel it electrically.

A wounded animal leaks charged electrolytes into the surrounding water, strengthening its electrical signature by approximately three times. This may partly explain why a great white that has made an initial bite will often withdraw and circle before returning — the prey's electrical field is intensifying as injury progresses, providing a more precise localisation signal.

The Hierarchy of Senses

Electroreception does not operate in isolation. Great white sharks navigate toward prey through a layered sequence of senses, each one engaging at a different range.

At the greatest distances — up to half a kilometre — smell is the primary sense. The olfactory system is extraordinarily sensitive: a great white can detect one part of fish extract in 25 million parts of seawater, and its olfactory bulbs are the largest of any shark species. A blood trail in the water is followed chemically, with the shark tracking the concentration gradient back toward the source.

As it closes to within a few hundred metres, hearing engages. Great whites are sensitive to low-frequency sounds, particularly the irregular, low-pitched pulses produced by struggling, injured, or spawning animals. These sounds carry well through water and provide directional information that smell cannot.

At around 100 metres, the lateral line system activates. This is a series of fluid-filled canals running along the body that respond to pressure changes and water movement — effectively allowing the shark to feel disturbances in the water at a distance. A seal swimming near the surface creates a pressure signature the lateral line detects long before the seal comes into visual range.

Vision takes over within a few tens of metres. But in the final moments before a strike — when the shark's jaws are open and the eyes have rolled back into their protective position, losing sight of the prey — electroreception is what guides the bite.

The system is not redundant. Each sense operates at its optimal range and hands off to the next. Electroreception is the terminal guidance system: the last and most precise sensor to engage before contact.

The Bump and Bite Explained

The behaviour commonly called the "bump and bite" — where a great white appears to nudge or graze a potential prey item before committing to a full attack — has long been interpreted as cautious investigation. This is partly correct. But electroreception provides a more complete explanation.

The ampullae of Lorenzini have a detection range of roughly a metre. At close range, the shark is actively reading the electrical signature of whatever it is approaching: the frequency, the amplitude, the pattern of the field. An injured fish produces a different signature from a healthy one. A marine mammal produces different frequencies from a fish. A human being in the water produces different frequencies from both. The "bump" is in part an electroreceptive interrogation — the shark getting its terminal sensor close enough to read the field clearly before deciding how to respond.

This also explains why shark deterrent devices that emit electrical fields are among the most consistently effective personal protection technologies available. By generating a field that overwhelms or interferes with the ampullae of Lorenzini, these devices essentially blind the shark's most precise proximity sensor at exactly the moment it matters most.

Navigation by Magnetic Field

The ampullae of Lorenzini serve one more function that is only now being fully understood: navigation.

As an animal moves through the Earth's magnetic field, the motion generates tiny electrical currents. The ampullae of Lorenzini are sensitive enough to detect these currents, effectively giving the shark a sense of its position and orientation relative to the planet's magnetic field. Research has shown that sharks can detect variations as subtle as half a millionth of Earth's total magnetic field strength.

This magnetic compass sense may explain how Nicole — the female great white tagged off South Africa in 2003 — swam 6,900 miles across the Indian Ocean to Australia in 99 days and then returned to almost exactly the same stretch of South African coastline. No landmarks. No visual cues. Potentially navigating by reading the planet's own electrical signature through the same organs that detect the heartbeat of a fish buried in sand.

What This Means in the Water

The next time a great white shark approaches a cage dive boat and appears to look directly at the cage, it is not just looking. It is smelling, hearing, feeling pressure changes through its lateral line, watching, and reading the electrical field produced by every person on the boat and in the water. It has more information about you than you will ever have about it.

This is not a threat. It is a reminder that the animal operating in that environment has been refining this sensory toolkit for hundreds of millions of years, and we are visitors in a world built around senses we do not possess and can barely measure.

White Shark Ocean operates cage diving and surface encounters in Mossel Bay — the best place in the world to experience these animals up close. Book at whitesharkocean.com.

Frequently Asked Questions

What are the ampullae of Lorenzini?

The ampullae of Lorenzini are a network of jelly-filled sensory canals opening through pores on a great white shark's snout and lower jaw. Each canal leads to a small fluid-filled sac lined with sensory hair cells that detect minute differences in electrical potential between the pore opening and the interior of the ampulla. The system allows great white sharks to detect the electrical fields produced by the muscle contractions, nerve impulses, and metabolic activity of other animals — with a sensitivity as fine as five billionths of a volt per centimetre.

How does electroreception help sharks hunt?

Electroreception serves as the terminal guidance system in a great white shark's multi-layered sensory approach to prey. At close range — within approximately a metre — the ampullae of Lorenzini read the precise electrical signature of the prey, guiding the final strike even after the eyes have rolled back to protect themselves in the moments before the bite. The system can also distinguish between different types of prey by their electrical signatures, which may explain the "bump and bite" behaviour observed when sharks investigate unfamiliar objects before committing to an attack.

Can great white sharks detect human heartbeats?

Yes. Every animal produces electrical fields as a byproduct of muscle contractions, nerve signals, and metabolic activity. Human beings in the water produce electrical fields within the detectable range of a great white's ampullae of Lorenzini. A shark approaching within a metre or so is reading the electrical field produced by the swimmer's body, including the rhythmic signature of the heartbeat. This is in part why erratic movement or rapid heartbeats — which alter the electrical signature — may influence shark behaviour.

How do electric shark deterrents work?

Electric shark deterrents generate an electrical field around the user that is strong enough to overwhelm or interfere with the shark's ampullae of Lorenzini. By flooding the shark's most sensitive proximity sensor with an uncomfortable or disorienting signal, the device disrupts the electroreceptive interrogation that typically precedes a close approach or bite. Research testing electric deterrents on great white sharks in South Africa found they significantly increased the time sharks spent at a distance and reduced close approaches, making them among the most evidence-backed personal shark deterrent technologies currently available.

Do sharks use electroreception for navigation?

Research suggests yes. As an animal moves through Earth's magnetic field, the motion generates tiny electrical currents that the ampullae of Lorenzini are sensitive enough to detect. This gives sharks an effective magnetic compass that may guide long-distance migrations. The extraordinary precision of tagged great whites — such as Nicole, who swam 6,900 miles to Australia and returned to almost exactly the same stretch of South African coast — is consistent with magnetic navigation via the same electroreceptive system used to locate prey at close range.