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. Hazards The unpredictability of sneaker waves and their tendency to arrive suddenly after lengthy periods of gentle, lapping waves makes it easy for them to surprise unwary or inexperienced beachgoers; because they are much larger than preceding waves, sneaker waves can catch inattentive swimmers, waders, and other people on beaches and ocean jetties and wash them into the sea. The force of a sneaker wave's surge and the large volume of water rushing far up a beach is enough to suddenly submerge people thigh- or waist-deep, knock them off their feet, and drag them into the ocean or trap them against rocks. Many coastlines more prone to sneaker waves lie in colder parts of the world where beachgoers tend to wear heavier clothing. The amount of sand and gravel in a sneaker wave can quickly fill clothing and footwear such as boots with sediment that weighs a person down as they are swept up a beach and then back into the sea, increasing the chances of drowning. Floating and rolling logs in a sneaker wave also pose a danger, as they can badly injure people as well as pin people down when they come to rest, and it can be difficult or impossible to move such a log before a person pinned by it drowns as later waves arrive and fill the person's lungs with water and sediment. Geographic distribution Sneaker waves are mainly referred to in warnings and reports of incidents for the coasts of Central and Northern California (including the San Francisco Bay Area's beaches, especially Ocean Beach, Baker Beach, and those that face the Pacific Ocean) (e.g. from Big Sur to the California–Oregon border), Oregon, and Washington in the Western United States. Sneaker waves also occur on