Waters off North Carolina’s Outer Banks are notoriously deadly, and a tragic example came to light when 73 sea turtles died in one day at Cape Lookout.

It happened Sunday, Jan. 21, when the N.C. State University Center for Marine Sciences and Technology collected 109 paralyzed sea turtles off National Park Service beaches.

“Unfortunately, only 36 of them survived,” the center reported in a Jan. 22 Facebook post.

“Deceased turtles will be necropsied and used for research. Surviving turtles are being examined and treated … before eventually being released back into their natural habitat.”

The official cause of death: cold stunned.

That occurs when sea turtles encounter a sudden drop in water temperature, which happens all too easily off the Outer Banks. The barrier islands sit at a turbulent spot where the warm northbound Gulf Stream collides with the southbound Labrador Current, experts say.

“During the fall and winter, sea turtles will migrate to seasonally warmer waters. … The water around the Gulf Stream can be colder, resulting in a severe drop in temperature,” Cape Lookout National Seashore reported.

“Turtles can become lethargic and hypothermic in the cooler water. They experience a condition called ‘cold-stunned,’ which inhibits them from swimming and eating. Winds and tides can eventually cause sea turtles to wash up at Cape Lookout.”

More than 300 cold-stunned turtles were found the first week of January at Cape Hatteras National Seashore, which is just north of Cape Lookout, the National Park Service reports.

The two national parks have teams that collect and transport cold-stunned turtles to veterinary facilities in hopes of saving them. The turtles often end up at the Sea Turtle Assistance and Rehabilitation Center at the North Carolina Aquarium on Roanoke Island to recover.

Tourists who find the turtles can easily assume they’re dead, but that’s often not the case, experts say.

“Turtles can appear lifeless but are often still alive. Do not try to put it back in the water,” the park says.

Anyone who finds a dormant sea turtle on a North Carolina beach is asked to call the NC Sea Turtle Standing Network Hotline is (252) 241-7367.

Hundreds of tires emerge from ocean off NC and float ashore. How did they get there?

Castle emerges from sand dunes at park in NC’s Outer Banks. How did it get there?

Extended warranty offer washes up on NC Outer Banks beach, proving there is no escape