Sneaker waves appear suddenly on a coastline and without warning;"Sneaker/High Waves and Log Rolls Can Be Deadly," National Weather Service Accessed 4 December 2021 generally, it is not obvious that they are larger than other waves until they break and suddenly surge up a beach. A sneaker wave can occur following a period of 10 to 20 minutes of gentle, lapping waves. Upon arriving, a sneaker wave can surge more than beyond the foam line, rushing up a beach with great force. In addition to containing a large volume of rapidly surging water, a sneaker wave also tends to carry a large amount of sand and gravel with it. It can be strong enough to break over rocks and float or roll large, waterlogged logs lying on the beach weighing several hundred pounds, moving them up the beach during the landward surge and then back down toward the ocean as the wave retreats. Sneaker waves appear to be more common along steep coastlines than in areas with broader, more gently sloped beaches.
