"The UT 3000 is the very first underwater communication system combining analogue and digital communication in one unit. In addition to the telephony and telegraphy mode, the UT 3000 offers unique features such as own noise measurement, horizontal distance measurement and transmission of SOS signals.
"The new digital mode for the first time allows fast and reliable transmission of digital data in water. The possibilities for digital data transfer are nearly unlimited. In the future, own position data, SMS, maneuver reports or target data can be exchanged between submarines in a more secure way.
Also: according to the UT 3000 MASQ brochure, it can transmit at up to 1000 bits/sec from 12km to 17km
Edit more: the brochure says the communication protocol overhead is typically 20%. Error correction is included - and features "excellent burst noise rejection". I would think underwater burst noise could be quite long. Would this require an interleaved code? Could someone comment on this?
"#deepseachallenge for the curious, using underwater audio coms UT2000/3000 at 8K freq to hear/talk to Jim five miles of water...30K ft now"