A frenzy of some 150 sharks is gathered along Israel’s coastline, said to be attracted by the warm water churned out by the Hadera power station. The dusky and sandbar sharks regularly appear off Israel’s Mediterranean coast at this time of year but the Israel Nature and Parks Authority (INPA) says this year’s swarm is the biggest yet.

Some eager Israelis wanting to snap a selfie-with-a-shark are setting out on dangerous diving trips toward the herd, prompting the INPA and the Israel Diving Authority to issue warnings about staying away from the area.

The INPA said that while attacks on people aren’t usually attributed to dusky and sandbar sharks, these endangered species are unpredictable and thus swimming up to them is unwise.

“Encounters with sharks are uncontrollable and can endanger both the divers and the sharks,” INPA told the Algemeiner. “This means it is forbidden to harm, disturb, feed or do anything else to them without risking criminal prosecution.”

Drone enthusiasts have also been crowding along the beachfront, flying quadcopters equipped with cameras overhead to film this unique sight.

Meanwhile, marine ecologists are trying to figure out why the sharks are even here. Shark populations have been decreasing in the Mediterranean Sea but every winter brings even bigger frenzies to Israel’s shores. Some scientists theorize that the warm water serves up more prey or that this is a mating juncture.

“We know they like being in the warm waters, but we don’t know exactly why,” Nature and Parks Authority marine ecologist Ruth Yahel told AFP. “You can see they’re drawn to the warm water—they enter its stream and perform a Rondo-like dance, fly out with the stream, circle around and do it again.

“The impression is they’re arriving here more.”