An intervention system and method for control of seabed equipment, including a control umbilical connected to a support vessel or rig via a surface winch; a tether connected to underwater seabed equipment; and an umbilical management system unit coupled between the tether and the control umbilical to couple the support vessel or rig to the seabed equipment. The control umbilical and the tether via the umbilical management system unit provide a communications channel for communicating media, including data, electrical power, hydraulic power and/or chemical treatment fluid, from the support vessel or rig to the seabed equipment. The umbilical management system unit allows for easy deployment and management of the control umbilical and tether and can reel in or pay out the tether and/or the control umbilical under remote control or autonomously.