Why does the British navy have glass bottomed battleships?

So they can see the German aircraft carrier.  It's not looking good for Germany in the Med.  Particularly with every ally on the board hanging out there in some capacity.  If I was a Libyan fighter pilot, I'd be very nervous right about now.  It doesn't look nearly so fortuitous for the allies on the other side of the world.  The navies are gone for the most part, so the US can't back  up the USSR, which has a fairly empty Eastern front.  Going to be a while before things shift that direction, but the Japanese will be land-bound for a while, at least in any significant concentration.