It's an ad for keeping water clean. She lists the physical qualities of water, then when she is dropping ink into the skull, she gives a statistic for the amount of people without potable water and the amount that die because they don't have it. I don't know enough French to translate her exact words.
It's a very effective ad, because we don't notice the drawing when it is just water, it is stable and just there, like taking water for granted, but as soon as the ink is dropped into it the water instantly changes a huge amount and we suddenly can't ignore it, as those who don't have access to clean water can't take it for granted.
Don't swim, float.