Yes, I saw the same article and it got me thinking.
From what I remember "Reliable Acoustic Path (RAP)" basically equates to a Direct Path detection but don't know what a Deep Reliable Acoutic Path is unless it is a deep ocean direct path detection.
I'm still waiting to see how someone solves the long-range, reliable, high-speed, underwater "wi-fi" communications issue. Seems like the physics of underwater sound makes this a hard nut to crack.
"The Defense Advanced Research Projects Agency put out a solicitation last year calling for proposals for something like an underwater wireless internet – a seamless communications system that would allow Navy assets to work together and share large amounts of data below the surface, without tethering to a cabled network. Existing products for wireless underwater comms are available, but only at low speeds (up to about 20 kbps for acoustic devices) or short distances (as much as 60 feet for 1 kHz radio waves, as little as six inches for the standard Wifi frequency of 2.4 GHz)."
