And 1 can easily convince 2 by showing how the water, even though it's transparent, has measurable effects: It makes images of things above its surface waver; it imparts more pressure as the fish descend; it provides more resistive force when the fish swim faster; it provides the mechanism to explain how currents can carry the fish great distances. If the fish get really ambitious, they can even leap out of the water into the air to see and feel the difference between being surrounded by water and not.The OP states:
The responses come down to two ways of looking at it:The former swims and wonders how the water cannot be known to exist; the latter swims and wonders how it can be known at all.
- Fish saying, "Look and see."
- Fish saying, "Water does not exist because it is not seen."
Now... can your "water" do any of that?