Good article and diagrams:
The diagram shows the longest the boys would be underwater is 30 meters. That’s 98 feet or the 32 yard marker on a football field. That’s not even two average US backyard widths.
Comparing map one and map two, the tallest height is 10 meters and the lowest 1 meter. None of the heights is 30 meters so that has to be from one end of the pool of water to the other.