Anchorage's very own Cook Inlet boasts the second highest tidal fluctuations in North America: 30 feet between highs and lows! The Turnagain Arm tide comes in so quickly that it sometimes produces a massive leading wave, called a "bore tide," which can sometimes be ten feet high. Adventurous locals have occasionally taken to riding this wave on a surfboard, paddleboard or kayak, and a good day can provide a 45 minute, five-mile ride. (Due to the speed of the wave's approach and the quicksand-like nature of Turnagain Arm's mudflats, a bad day can provide massive injuries or even death. This is why I have never even batted around the idea of trying it myself!)
You gotta check out this amazing video: The Longest Ride.