In 1969 Hubbard replaced the Mud Box Brigade with the Rehabilitation Unit, again intended for those removed or disciplined "as ineffective or trouble."

The Rehabilitation Project Force developed out of a predecessor group, the Mud Box Brigade, aboard L. Ron Hubbard's private fleet in the late 1960s.

The Mud Box Brigade was assigned to clean out the mud box as well as fuel lines, water hues, bilges and so on.

The mud box is a small perforated screening box fitted to the suction pipe in the bilge of a ship, and is designed to catch larger solid waste before it can choke the pipeline and potentially damage the pump.