Only in the Netherlands

When I comment with Dutch people that there is an excess of signs everywhere in the country they seem do not have a clue about what I am talking about. Please have a look at this one below and judge yourself.

What do you think the sign above means ? Choose only one option.

a) Attention, water. You may drown.

b) Attention, water. You may drown.

c) Attention, water. You may drown.

d) Attention, water. You may drown.

(Picture taken nearby a small pond in the Zaanse Schans)