I am not actually convinced that is done with VFX but that they likely used 2 different types of powders of the same colour - one that washes away and one that does not so the water literally 'reveals' the text
Do you know how track mattes and 3D tracking work in After Effects? It wont' be an easy thing to create using just After Effects but I'll put it onto my list of things to do I just can't guarantee when I might get around to it.
Cheers,
Tobias
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