What I have heard is that this amount of water would be so heavy that the glass would have to be impractically thick.
The thought occurred as well.
In most modern buildings, the floors are made of reinforced concrete. While it is often assumed the concrete is over a metre thick, in actual fact most of it is little more than 200mm. The problem is, the floor needs to be strong enough to hold the load, and some, plus the weight of the materials which make the floor.
The weight of the water in this pool will be 375,000,000 kg. even assuming 20 people, each 2 metres tall and weighing 130KG, (ie big and fat) that would only add 2600 KG, not really significant.
So the structure would need to be capable of holding 375,000,000 kg plus its own weight. Structure includes the pool itself and the supporting walls and their buttresses.
Those bricks simply won't do the job.
