Hi all, I am attempting to create a pool of water graphic (divided into 9 equal parts (ie. 3x3 grid)) for a fishing game and would like to know how I would go about applying a grid to the space so I can refer to any of the 9 spaces.

Code:
import java.awt.*;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Pool extends JFrame
{
    public Pool()
    {
        setTitle("Carpet Fishing Game");
        getContentPane().add(new FishingPanel());
    }
    
    public static void main(String[] args)
    {
        Pool frame = new Pool();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500,500);
        frame.setVisible(true);
        
    }
}

class FishingPanel extends JPanel
{
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        
         Color water = new Color (0, 100, 200);
         g.setColor (water);
         g.fillRect(100, 100, 300, 300);
    }
}