HYSWAS anyone?

It isn't. I recall seeing this years ago. The buoyant "tube" (normally in a SWATH) is the foil ...loadssssssssssssssss of drag

 

That "thing" was called HYSWAC. We designed the huge trailing edge flap system with all the control and hydraulics to operate it; there are actually machinery spaces in that foil, with, in addition to the gearboxes and props, hydraulic power units, valve manifolds and assorted other things.

The old USN testcraft SES-200 was the 'victim', or trial horse, used to test out that 'foil'..the foil actually called a 'lifting body'. There was also a large "H" foil system mounted back on the sterns that used conventional lifting foils for flight control and balance.

It 'flew' well and achieved something around 35 knots. The trials period was very short though and not much done with it.

 

We also built and tested a twin-body variant of the lifting body concept...this one saw a lot more test and trials time and performed very well in terms of seakeeping.

 

That's it, some how, I thought you'd know

Saves me digging out my old Journals/files....i knew it had some HYS-acy type acronym.

 

No wonder the hull above the lift foil looked so weird, and so light also. I first took it for a weird looking 2 strut SWATH experiment in the 165 foot range...blind men and elephants...