Combined Active Passive Towed Array Sonar, CAPTAS-4 in operation from a French Frigate. There are also smaller/lighter versions of the sonar.
Defense One reports on a presentation at Surface Navy Association,
“At the Surface Navy Association conference in Arlington, Virginia, this week, the company showed off a video of the technology being installed on a commercial ship within 48 hours, turning the vessel into an anti-submarine “asset,” Bock said.”
While mounting the sonar on merchant ships might be useful, wouldn’t it make sense to mount it first on Coast Guard National Security or Offshore Patrol Cutters that could also host an anti-submarine helicopter and are already equipped with Navy compatible secure communications?
On a cutter or a merchant ship there is the question of who would man it? Every year trained personnel, including sonar technicians and ASW helicopter flight crews, leave the active-duty Navy and become part of the Reserve. Upon mobilization, they can be recalled to active duty to man these systems.
Chuck Hill's CG Blog 
Captas-4 Compact was designed to fit in the planned footprint of an LCS module, just weighs more than LCS module design which was absurdly light. That’s why Raytheon’s was in 3 sections spread all over the mission bay, to manage the weight the crane can handle. The Coast Guard should be able to place one by crane over the aft boat launch on NSCs if they had the need.