<stdin>

#define WATERHEIGHT 16

int x, y, offset;
for (x = 0; x < levelwidth; x++)
{
    offset = random(0, 1);
    for (y = levelheight-WATERHEIGHT-offset; y < levelheight; y++)
    {
        if (level[y][x] == AIR) { level[y][x] = WATER; }
        else { break; }
    }
}