Re: What does the hypothesised second form of liquid water look like?

It is thought that there are actually two forms of amorphous water/ice -- 
a high-density form and a low-density form.  You can find some more info 
by Googling on "amorphous water" or "amorphous ice".  Both forms 
are "glassy" -- they really want to become crystalline ice but are too 
cold (around 130 or 140 K) to get to that equilibrium state, so they are 
stuck in this glassy state just like window glass.  If you are near a 
library that gets Physics Today, you can read the cover story in the June 
2003 issue that is about these matters.  Unfortunately that article does 
not seem to be available on their Website.

As for what it looks like, I don't know if you mean microscopic structure 
or visual appearance, so I'll try to say something about both.

As I recall (from the talk I saw about it 2 weeks ago), the microscopic 
structure of the low-density form is similar to that of liquid water in 
that the water molecules hydrogen bond to each other in a mostly 
tetrahedral structure.  For the high-density form (which occurs at much 
higher pressures), they are jammed together tightly enough that they can 
no longer maintain the tetrahedral structure.  An analogy would be if the 
tips of the fingers on your left hand all attracted the tips of the same 
fingers on your right hand, but the palms repelled each other.  At low 
pressures, your hands would adopt a configuration with the tips touching 
but the palms apart.  Now imagine a high pressure, somebody shoving your 
hands together.  You could end up with your fingers interlaced and your 
palms closer -- not the configuration normally favored but forced by the 
high pressure which makes the volume become less.

As for visual appearance, I didn't find any information on that -- because 
of the high pressures involved, many of the studies are in sturdy pressure 
vessels that you can't see into.  It would be unlikely to have a color, 
because that is almost always a property of the individual molecule and 
one still has H2O molecules here.  My guess is that both forms would be 
similar to normal ice, which would mean clear or white (think snow) 
depending on whether there was any microscopic structure with a similar 
length scale to the wavelength of visible light.