It's real, but the people who read this are going to completely misunderstand how it works and what it is capable of. It's measuring surface acoustic waves on the water. Terahertz frequency signals cannot penetrate very far into the water so they aren't using it the way all those "scary" articles and videos of WiFi seeing through walls bullshit suggest. What it is capable of is essentially detecting infrasound, very long wavelength sound waves. I suspect it will have many issues with false signals, background noise from the environment and a huge amount of data analysis to make it even remotely useful in the field. It will be a slightly better sonobuoy type detector until they work out the massive data analysis problem. Until then, they will still have to use other methods of submarine detection with it. It's just a fancy microphone not an imaging system that sees through water. I'm sure we have something similar.