Machinery and methods are described whereby a free flying, remotely operated vehicle (ROV) can safely capture and take on board lightly managed seismic sensor devices (payload) while they are in-transit via a surface vessel in a (deep) water column. ROV payload can be replenished without the need for the ROV to return to the surface vessel to receive additional payload and to do so without the need for heavy launch and recovery machinery. The reverse process of returning payload from the ROV to the surface vessel is also disclosed.