1)What is considered to be surface?
the row with y == h + 1 or any cell out of cave?
What that?
1 2 1 1 1
.
.

2)May water flows not only from the higher row?
3 3 2 2 1
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...
...
?

I dont know what leads to my wa11 ( any hints?

In my ACed solution:
1. Only row with y = h + 1.
2. No.