A Schindler-Patalas plankton trap made of Plexiglas. The top and bottom doors open as the trap is lowered down to the desired depth. When the lowering is stopped, the doors close and trap the plankton in the sampler. After the trap is brought to the surface and lifted out of the water, the plankton are collected as water flows through the net attached to the side of the trap. Photo by Ray Drenner.