Deep-sea exploration is the investigation of physical, chemical, and biological conditions on the ocean waters and sea bed beyond the continental shelf, for scientific or commercial purposes.

Because electromagnetic radiation cannot penetrate any significant distance into the sea, the oceanographer uses acoustic signals, explosives, and earthquakes, as well as gravity and magnetic fields, to probe the seafloor and the structure beneath.

Only slightly more than 23% of the seafloor has been mapped in great detail, and even less has been explored with underwater cameras or submersibles. Mapping the seafloor is the first step in exploring the unknown depths of our global ocean.