I made it as a high school project.
Instructions to use the program: Download and open Map.jar file. A map is randomly generated when you click on one of the two options. Click on a white square (whichever square is not green), program will fill and span all white squares that the water can reach from the square user clicked. The squares will be filled with either lake water or ocean water. Lake water or ocean water is used depends on if the white squares spans to the edge of the window or not. Enjoy.