Frontispiece. The seafloor instrumentation that is part of the borehole geophysical observatory NEREID-2 (ODP Site 1151) as photographed by the JAMSTEC remotely operated vehicle (ROV) Dolphin 3K in September 1999. The polygonal-shaped object at the bottom of the photograph is the top portion of the reentry cone. The battery frame sits on top of the reentry cone and contains the batteries and storage acquisition module (SAM). The riser assembly, which is the top part of the borehole instrument string, passes through the middle of the battery pack. The borehole instruments are connected via four cables to the multiple-access expandable gateway (MEG), which is a stainless steel canister filled with electrical components that sits on the riser (both the MEG and the riser are visible at the top of the photograph). The bright lever at the top of the battery frame can be used by the ROV to eject the SAM. The slanted protective cover on the SAM is removed by the ROV to allow access to a temporary recording and communication device, referred to as the back from ocean bottom (BOB) module. The handle to the left of the lever is an underwater mateable connector that connects the MEG to the battery and to the SAM unit (yellow cable lying on the gridwork). The ROV makes this connection, thus providing battery power to the borehole instruments. The large circular holes in the gridwork allow access to the battery anodes, which can be replaced by an ROV when consumed.