Shawn
I thought it looked like a paper towel, then I saw your bubbles tag. I can't guess!
jokele
I think I have seen it somewhere. Looks like foam. But the big bubbles don't look like foam... I don't know. Please resolve the riddle sometime :)
Satoshi T
I think it is water on the enamel sink including air bubbles.
airey
@Shawn@jokele and @Satoshi ! Satoshi posted good answer :D It is fantastic that you guessed proper answer :)
Shawn I thought it looked like a paper towel, then I saw your bubbles tag. I can't guess!