This reduced visibility can hamper coastal surface operations and cause potential dust-related aircraft engine problems at sea. Terrain can force a wind direction change that may cuase low-level turbulence from wind shear between wind above terrain and wind between terrain. Fresh, often colder and less dense water enters salty, often warmer, denser water as a surface or subsurface plume, eddy or lens. Bottom sediment changes drastically due to sediment load and sediment and current flows increase. Increased current flow can affect amphibious craft and swimmer navigation.
Reefs predominate in tropical areas and are often unsurveyed.
All three can affect approaches taken by amphibious craft, swimmers and torpedoes, and can adversely affect active sonar. Most shipwrecks occur near shore. These hulks can present a hazard to navigation, but a bottomed sub can merge her signature with a shipwreck to escape detection. Light is produced when plankton organisms are disturbed with no correlation to weather or sea state. It can be observed from the surface to 35 feet.