The Anchorage Fire Department is warning people not to try and walk from the Anchorage shore across to Fire Island.

Authorities say that too often, attempts turn deadly.

Anchorage Fireman and their partners from Ted Stevens practiced water rescues Saturday afternoon. They were working with jet skis and a boat.

AFD says in the summer, people will try to walk across Cook Inlet to Fire Island, get trapped by the rising tide and end up in the water.

It’s not the depth of the water that proves fatal, authorities say.

“The challenge isn’t their ability to swim,” says AFD Battalion Chief Mike Davidson. “It’s that the water’s so cold that they really can’t successfully swim in it for any length of time. So, generally, when the victims attempt to enter the water they become incapacitated. And again, if they try to remain on the mud flats between the two parts of land, eventually they become entrapped by rising water and they have no choice but to end up in the water.”

AFD says people have died attempting the crossing. Even though AFD trains to rescue people who get stuck, they can’t always be there in time, which is why authorities discourage anyone from trying it.