Author: O-le_o-le
Fill some cells with water so that the numbers at the borders indicate how many cells in the corresponding row or column contain water. Within an area, the cells must be filled up from the bottom up. Within a row of an area, all cells must always be filled with water or none (even if there are other areas in between).
Grid control: Click the mouse button at the selected cell to change the color of the cell. Second click will put auxiliary cross sign, which doesn't affect correctness of the solution, but helps visually. You can also drag the content of one cell to another with the mouse. More details about grid control are at the help page.