A riser disconnect/reconnect system including a disconnection package (RDP) and a modified lower marine riser package (LMRP) are provided for quick disconnection of the marine drilling riser (MDR) from the LMRP. The RDP includes a flex joint and a release connector (RC) with a mandrel that engages a modified LMRP. In an emergency event, the RDP is disconnected from the LMRP allowing access to the BOP stack for emergency intervention. In routine drilling operations, the RDP is disconnected from the LMRP facilitating the recovery of the LMRP or BOP stack to the surface for repair or maintenance without recovering the MDR. The RC joins the flex joint to the uppermost annular blowout preventer in the LMRP. The RC is configured for use in a standard or inverted position. Also provided is a mechanical locking connector, a resident ROV and sonar technology and methods of using same with the RDP.