The stealth aspect of rebreathers may no longer be as effective.
New Electronics Magazine writes:
PCB design services company Dayford Designs has completed a series of boards for use in QinetiQ’s Cerberus 360 swimmer detection system. The project included a 12 layer, high speed data communications board and a 12 layer a/d conversion board using microvia technology.
Cerberus 360, developed to provide protection for ships and harbours, uses wideband sonar technologies to detect intrusion by swimmers using snorkel, scuba or rebreather, as well as swimmer delivery vehicles. The system has a detection range of 1.6km.