Thanks a lot Barta.
I think I have an answer:
When they go to the cliff, they look down in the water and so they can see themself reflecting in the water. By doing that they can see if they have a dot or not. Is it correct?
No reflection in the water: God took away ALL means by which they could see themselves, so that includes water.
(As HandEFood pointed out already <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" /> )
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