This is a common practice for increasing the depth of streams, lakes, bays or reservoirs by scraping and removing solids (such as sand) from the bottom, which usually comes before the development of ports, breakwaters, yacht marinas, etc.

This process, however, produces large amounts of particulates which remain suspended in the water for long periods, effectively blocking sunlight from entering deep into the sea and shading species dependant on light for photosynthesis. The water usually turns a milky white, as a result.