They are all unambiguously H[sub]2[/sub]O, however. They’re substantially the same, but different individually—different ‘modes of presentation’ of the same thing, perhaps. You can make sense of the trinity in the same way—the Father, Son, and the Holy Ghost are all God, and there is only one God, in the same sense there is only one H[sub]2[/sub]O, but they’re different ways the substance of God may present itself, just as there are different ways H[sub]2[/sub]O may present itself, as a liquid, as a solid, or as a gas.