Sheet piles are interlocking panels driven into soil to form a waterfront protective structure often called a "seawall" but properly known as a "bulkhead".
This video shows sheet piles being driven using water to soften soil and facilitate pile installation.
This image shows a sheet pile bulkhead in a harbor. To protect against impact from vessels (or other sources) wood fender piles have been installed against walers that will help spread the impact force over a wider area, helping to avoid point loads on the sheet pile wall. A wall cap will be installed and the excavation will be backfilled.
Sheet piles can have a variety of interlocking profiles and are typically made of UV-resistant vinyl (often PVC), metal, concrete, or fiberglass-reinforced polymer.
Concrete sheet pile installation.
Steel sheet piles
Without cathodic protection, galvanic (electro-chemical) corrosion can destroy a steel bulkhead.