A method is proposed for defending shore establishments and sea vessels from acts of overt and covert intrusion by human swimmers across defensive perimeters. The basic interdiction device is placed in the water at the facility to be defended, and delivers a high intensity, directional acoustic emission which is capable of deterring a swimmer at an adjustable range of from 20 to more than 200 yards from the device. Alternative means of producing the emissions are presented, with progressively higher intensity, increasing flexibility and escalatable capability for human intruder deterrence. Methods for enhancing the deterrence effects are proposed. These improvements can extend deterrence capability well beyond I,000 yards. The interdiction device and supporting equipment, including intruder detection, monitoring and tracking equipment can be packaged in light-weight portable components, for rapid deployment and quick relocation to a new facility.
