Turnagain Arm Tidal Bore

The Cook Inlet in Alaska branches into two arms, the Knik Arm and the Turnagain Arm, one on either side of Anchorage.  The shallow waters of the Turnagain Arm is one of a few places in the world that produces a tidal bore.  A tidal bore is created in areas with large tidal differences, when an incoming high tide encounters water still draining out from the previous low tide. This can cause a disturbance ranging from barely discernible to a substantial wave during the right conditions (up to 6 feet in the Turnagain Arm).  We observed three different tidal bores while we were in the Turnagain Arm area.

We even found people trying to ride them.