A sill is a low profile rock structure placed parallel to the shore so that a marsh can be planted behind it. These structures can be used to protect/control a wide range of habitats & energy levels creating a natural buffer & preserve for benthic shallow water organisms.
A breakwater is a strategic offshore barrier built out into a body of water to protect from the force of waves, thereby preventing coastal erosion & providing a calm harbor for boats to drop anchor.Breakwaters can also be small structures designed to protect a gently sloping beach by being placed offshore in relatively shallow water.
A revetment is a sloping structure placed on a river bank or steep shoreline that absorbs the energy of incoming water to reduce erosion. There is often no buffer between the upland & the revetment that allows the filtering of runoff &, in most cases, no vegetation occurs shoreward of a revetment. They are the effective “last line of defense” in high energy environments.