hmmm
So, apparently the standard audio range frequencies transmit well in water, they're just loud and somewhat obvious outside of water. My tech guy (who's playing the technomancer) says that they transmit at one magnitude worse than ideal, but the time shift is one magnitude, so we'll be at a good level.
Here's my current line of thought.
My RCC, this has to be a custom job, and will be my second. Obviously it will be Scratch Built Junk. A bathysphere, basically, air coming from a facility in the Deep Lacuna. I've got ties to Ares, so Knights Errant might work with me on it even, if I help them when need be. It transmits out on the frequencies below human audible range, but other creatures will hear it.
Screamer Drones, they receive the sub-human audible levels, and transmit on the human audible levels. If they weren't underwater, and were being used in a populated area, people might think its a goblin rock concert gone mad.
Good luck hacking them, they operate on a signal that nobody else uses. Eventually, sure, the smugglers will figure out what's what, but until then...