"Long leads are usually stored in figure-of-eight loops on specialist baskets or frames, which are landed on the seabed mid-way between the two end destinations. The ROV flies in with a tooling interface and collects each end in turn and drags it to its destination."
Deepwater installation of electrical and hydraulic Flying Leads by Workclass ROV systems. Very informative paper on the whole process. Technical Paper: May 2005 - OTC (Offshore Technology Conference) OTC paper presented May 4th. "Making All the Right Connections." Addresses the deepwater installation of electrical and hydraulic Flying Leads by Workclass ROV systems. http://www.perryslingsbysystems.com/download.cgi?id=1045
You'll see the same deployment frame here as well.