Surviving the Night Shocker
A commercial oil field diver using surface-supplied air was inspecting a minor oil leak in a deepwater pipeline at night. As he swam along the line, the surface tender heard a few stammered words on hardwire communications: “fish … electric.”
The diver’s helmet camera image froze, framing the seafloor, and the tender could not get a verbal response. The support vessel immediately deployed a safety diver, who found the commercial diver unconscious on the bottom, with his helmet flooding and filled with vomit. He likely would not have survived if he had been on scuba.
The safety diver pulled his unconscious partner to the surface and got him into the ship’s recompression chamber. The diver was conscious by the time they got to the hospital ashore, where he was treated for atrial fibrillation and recovered normal heart function.
The helmet cam footage revealed the mystery culprit: A large, pancake-shaped electric ray approached the diver just before he lost consciousness. Four electric blasts registered as static bursts on the monitor.
The Western Atlantic torpedo ray (Tetronarce occidentalis) is a giant species among rays, reaching up to 6 feet (1.8 meters) long and more than 200 pounds (91 kilograms). It is also the heavyweight champion of electrical output at up to 220 volts and 30 amps, which is enough — although unlikely — to kill a human.
Torpedo rays are stealth predators that bury in the sand in the daytime and emerge to hunt fish at night. Their body disk houses kidney-shaped organs composed of modified muscle cells in each wing that act as giant discharge capacitors. Torpedoes pounce on their prey and release a rapid series of current discharges, causing nervous system collapse. The current is strong enough to cause muscle contractions that snap the spines of prey fish. The ray engulfs the prey head first, accommodating the meal in its capacious stomach.
I have studied the enigmatic species for 32 years and tagged more than 100 animals while on scuba dives, using hydroacoustic tracking tags to reveal some of its natural history. These rays were once rare in the North Atlantic off Nova Scotia, but over the past 15 years, as seasonal water temperatures rise faster and stay warm longer, we have seen torpedoes in numbers never documented anywhere. My record in one day was 14 animals of both sexes in an area the size of a tennis court.
We have made many new discoveries while studying this species, including new behavior and movement findings. A ray tagged near Halifax, Nova Scotia, traveled over three months, covering more than 685 miles (1,100 kilometers) deep into the North Atlantic before its tag released, revealing for the first time that this species has an inshore, shallow-water phase and a pelagic phase in its life cycle. I also documented extensive use of passive gliding, allowing them to soar and migrate upstream and downstream in currents by bending their body into a hydrofoil.
The day-to-day research work of diving to study a potentially lethal and largely unknown species has been fascinating. We carry oxygen and an automated external defibrillator (AED) on the small boat we use for fieldwork and adhere to Canadian Association for Underwater Science research diving standards. I use a nonconductive tagging pole with a detachable, biocompatible tag tip inserted under the ray’s skin.
The rays are generally hard to spot when buried in the sand, and it takes some time to develop an eye for locating them. Using a housed video camera with a set of parallel green lasers, I lay the tagging pole on the bottom next to the ray and position myself 8 feet (2.4 m) above it to record its size. Then I swim around to the tail end and record the presence or absence of male claspers by gently lifting the tail with the pole.
Finally, I tag the ray from behind, generally on one side of the tail close to the first dorsal fin. Most rays react very little to this procedure, and I can often complete the entire process without the ray leaving its burrow.
I have had some revealing interactions with the rays. On several occasions I learned they tend to attack certain electronics. One time it was the strobes on a buddy’s twin lighting kit. The trigger appeared to be the whining sound and the strobe’s flashing light as it recharged, which led to about 20 seconds of concerted attacks, including repeated bites on the strobe.
On another occasion, a friend who did not realize he had found a torpedo had uncovered one by fanning it, and then he got in front with a video camera to record his find. The irritated ray launched itself at him, the viewfinder filled with the underside of the animal as it hugged his head, and a prolonged scream provided the soundtrack as he was repeatedly shocked. Fortunately, he survived.
I was attacked twice in rapid succession while using a GoPro on a short stick. I had neglected to turn off the camera’s flashing blue signal light, which cut through the poor 10-foot (3-m) visibility to the ray I was recording. I heard my buddy grunt; when I looked up, a rapidly swimming second ray appeared out of the murk and collided with my chest. It hugged my arm and emitted several good zaps.
I dropped the camera, which the ray chased before vanishing into the murk, followed by its friend that I had been recording. I picked up the pole and followed them, but within seconds I was attacked again in the same way. The ray stopped as soon as I let go of the pole.
What linked my experience with that of the commercial diver was that light and electronics appear to be common attack triggers. Elasmobranchs like rays and sharks commonly use electroreception and vision — along with other sensory modalities such as the acoustico-lateralis system and scent — to detect prey. It may be that the settings of some electronic equipment mimic the weak electric signals that fish emit. It appears likely that the headlight on my dive mask, my video lights, and associated electronics are attack triggers, whether predatory or defensive.
I have also been on the bottom, close to rays, and felt a gentle warning tingle when within a few inches of them. Documentation shows that torpedo rays can modulate the amount of electricity they deliver, depending on whether they want to stun or kill. That makes sense from an efficiency standpoint, as it appears to take much more time and energy for the ray to regenerate its ability to shock after a large discharge.
I have gained a healthy respect for this species through hundreds of dives over 30 years. Recent evidence suggests that many shark species shun electric rays for obvious reasons — it’s likely similar to eating an electric fence.
If you encounter a torpedo ray, keep a safe distance and have an evasion plan in place. Being ready to rapidly swim away and upward is an essential skill when encountering torpedoes. They can change from seemingly lethargic bottom dwellers to fast, persistent pursuers in a heartbeat.
Avoid the front end of this animal, since they shock from the front, between the wing tips. Being directly behind them, however, is no protection against an attack. They can rotate upside down to turn and spin in milliseconds, allowing them to come right back at you, and likely not in a good mood.
There are several case reports of divers who have lost consciousness when shocked by torpedo rays. Some divers have experienced cardiac arrhythmias after being shocked and required cardioversion to restore their normal heartbeat.
The bottom line with the increased inshore occurrence of this species in the North Atlantic is that if you encounter one, don’t poke the proverbial bear — or in this case, the ray.
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Learn more about electric torpedo rays in these videos.
© Alert Diver – Q3 2026