Each of us has a different image when asked about “ocean waves”. These vary from serene and peaceful to wild and violent. We will ask “what is that all about” for the four main classes of waves: swell (for surfers), seiche (maybe in the ship’s swimming pool), tsunamis, and tides. Alaska is the source of major tsunamis. Alaska also has some of the largest tidal extremes in the world. Why is that? In all four types of waves, the water goes “up and down” - but in very different ways and for different reasons. For trips to Alaska knowing more about tsunamis and tides is essential!