ISProgram
SketchUp Orbinaut
That might be well and good, but you get those advantages to a maybe lesser, but still by no means insignificant degree for any air-launched or floating system without combining the too, and it still doesn't explain why anyone would want to submerge a rocket, filled with potentially cryogenic propellant and sensitive technology, in salt water for what has to be at least an hour, probably more, before launch.
I would also like to mention, that, looking at the launch video, the Haas' payload fairing (or at least most of it) is underwater. Why risk saltwater contamination of the potential payloads for the Haas' with this architecture?
I would also like to mention that I don't think the Haas' payload fairing will even maintain integrity, given that the IAR-111 will have to accelerate to at least >100mph to liftoff in a medium that's 2,500 times denser then air. The Haas' front end will be taking the brunt of all this, since it will be submerged in said medium.