These are various ways of exploring for abyssal ore nodules, include seismic surveying with an airgun (1) and a string of hydrophones (2), echosounders (3), grab samplers with cameras attached to them (4), oceanographic probes like the bathysonde (5), dredges (6), deep-sea cameras (7), and wire-bound samplers, such as the box corer (8).
Manganese nodules are concretions with diameters averaging 4 centimeters (2 inches) that occur in red clay and ooze on the floor of the Pacific Ocean, with the major concentrations around the Samoan Islands. They contain high concentrations of manganese. They are thought to have formed as agglomerates from colloidal solution (colloid) in the ocean's waters. The commercial mining of the nodules is being delayed by legal controversy over international rights to this valuable mineral resource. Although commercial lies in the future, but work is centered on two systems – hydraulic suction dredges and mechanical dredges.