yah the launch would be a wild ride with the lines attached to the steering.
Here was a good response from another friend on this:
As an engineer, I don't believe the "Nereus" can be ridden with any real control save for straight downwind, in which case it would be like many of the towable personal submarine crafts that can be manuevered with vanes and use a simple joystick to control. They are designed to be nuetrally bouyant, and my Dad built one back in the 60's that we played with behind our sailboat down on the Chesapeake Bay. You could dive down to about 20 feet with it holding your breath. He would put on a scuba tank and cruise around back there for 10 minutes sometimes.
I could see something like that working with a kite, but once you got to any depth, I would think losing control of the kite would be imminent.
Here's a strange link I found poking around on the topic : a towable underwater towable "kite" patented in Australia awhile back:
http://www.wipo.int/pctdb/en/wo.jsp?IA= ... SPLAY=DESC
So, in summary on this Nereus thing . . .
As an engineer, I don't think the thing will work.
As a kite enthusiast, I would love to be proven wrong.
As a gambler I'd like to bet against it.