It's great to see that the idea is now getting notice. It really is much more cost effective than sending manned vessels. People are expensive and it takes a lot to keep us alive.
Currently, the most efficient way to map involves the use of multibeam sonar, which sends pulses of sound that bounce off the seafloor and back. Autonomous underwater vehicles can also be used, though they are less efficient. At the meeting, Mayer floated the idea of an unmanned barge, equipped with multibeam sonar, that could roam the seas while continuously mapping, which would cost about one-third as much as a manned vessel.I wouldn't say "barge", but things like Argo floats could be made larger and have single beam sonars.
Also, it would be great to have larger ships have depth sounders that were capable of deeper water, but that is tough with the shipping industry having such thin margins and massive ships lasting as little as 11 years before they are sent to the breaker.
I was sure that I had written about this someplace before, but I can't find it. I need to snap a picture of my early thoughts on the topic and add it here. Some of which is totally irrelevant now. If you used a wave glider type system, there is no need for propulsion.