Square waves are a dangerous marine phenomenon that occurs when two wave systems intersect at perpendicular angles, forming a grid pattern on the water's surface. This effect, caused by the interference of different wave fronts, generates unpredictable currents and turbulence that pose a significant risk to both swimmers and boats. The difficulty in staying afloat and changes in the maneuverability of ships can increase the risk of accidents or sinkings, especially in small vessels. While their appearance may be fascinating, these marine conditions underscore the importance of caution and knowledge of the ocean's hidden dangers.