A new method has been developed for installing piezometers in the sediments of deep harbors and lakes, where it has been difficult to measure hydrogeological parameters and collect pore waters for geochemical analyses. Using an underwater hammer operated from the surface, piezometers have been installed as much as 12 m below the water-sediment interface. The piezometer screen is held in place by barbs on the drive head and is connected to the water surface via flexible tubing. These piezometers have been installed from boats and from ice cover in water up to 30 m deep. However, installation in water more than 100 m deep should be possible. ¿ American Geophysical Union 1996