For example, the Smith-Macintyre grab is lowered from ships, and on contact with the seabed, a cylindrical bucket is triggered which scoops up about 10 litres of sediment. Another, the Van-Veen grab, is like a giant pair of tongs which closes together as the winch draws the cable in. Sediment is then evenly scooped into the large buckets. A box core uses trigger plates to close the top and bottom of a metal box plunged into the seabed. This device neatly extracts a plug of sediment that is mostly undisturbed and allows scientists to examine the layers of sediment carefully.

Sediment samples can tell scientists a lot about the ocean above the seabed because of the particles that drift down through the water column to the seafloor, and also about the geology that lies beneath the seabed surface. For example, sediment samples can be used to measure the grain size, limestone or silica content, trace element and nutrient levels. These are basic measurements of the seabed which are just as important as if describing the characteristics of soils on land. As well, much of our knowledge about the animals that live in and on the seabed have come through looking at the rocks and mud collected by sediment grabs. Worms and other sediment-feeding animals make their homes in the seabed and a grab is often the most simple device used to collect them.