Use gravity and water to sink your dock posts ( #pilings ) 3 feet into the mud. Order a higher grade of exterior pressure treated wood from your lumberyard called "Critical Structure" - It's a grade above "Ground Contact". Simply tie into your lawn irrigation pump. These powerful pumps create enough volume and pressure to get the job done. Normal house water pressure is not enough. Sandy soils work best. If you have clay (like we did) plan on spending a little more time. Create a waterjet nozzle