Turnagain Arm's Tidal Bore

The Turnagain Arm of Alaska's Cook Inlet in the southern part of the state experiences a natural phenomenon known as a tidal bore. When the tide comes in, a wave 7 ft high, moving 12 mph comes rumbling up the Turnagain Arm creating an extreme sport opportunity for kayakers, paddleboarders, and surfers. A tidal bore is caused when a large influx of water from an incoming tide is moved up a narrow channel. The water causes such a degree of turbulence that a low frequency rumbling sound is generated that can be heard quite a distance away.

Source: Wikipedia