When the moon tugs at the tides here in Cook Inlet, Alaska, a gravitational event known as a bore tide occurs, pushing waves up against the current and creating a watery playground for stand-up paddleboarders. The bore tide here in Turnagain Arm, near Anchorage, is one of the biggest in the world, sometimes creating waves 10 feet tall. The biggest waves occur after an extremely low tide, as that’s when the largest amount of seawater comes rushing back into the narrow bay. Surf’s up, Alaskans!