Easily sample most types of bottom surfaces. Constructed from stainless steel and powder-coated carbon steel for corrosion resistance. The top of the sampling chamber is screened to allow water flow during deployment and reduce the frontal shock wave that may displace sediment as the dredge contacts the sample surface. A two-way spring-loaded mechanism activates on contact with the bottom, no messenger is needed. Sampling area is 6'' x 6''.