The Turnagain Arm — the long fjord-like inlet that Girdwood sits on — has the second-highest tidal range in North America, second only to the Bay of Fundy. On the strongest tides, the rising water races up the inlet as a visible wave, the bore tide, which can be watched from several pullouts along the Seward Highway between Beluga Point and Girdwood.
The best viewpoints are at Beluga Point and Bird Point, both signed off the highway and both with parking and information boards. Time your visit using the Anchorage bore-tide schedule, usually 2 to 2.5 hours after Anchorage low tide. Beluga whales sometimes follow the wave up the arm in summer.