How do I make it so that I can move up and down along the global y axis?

this is my script for moving the player, im making a Subnautica demake so this is for swimming. I can swim towards wherever the camera is facing, but i also wanna be able to swim up and down along the global y axis and I can't figure out a way to do it, any help would be greatly appreciated.

this is a code snippet making the player move from my movement script, i apologize if it's bad, I'm not very experienced.

Code (CSharp):

1.  
2. //vertical is the w-s axis
3. //horizontal is the a-d axis
4. //Cam is the camera
5. //mouseY is mouseInput along the Y axis
6. //mouseX is mouseInput along the X axis
7.  
8. void Update()
9. {
10.       if (Input.GetKeyDown(KeyCode.Space))
11.             {
12.                 goingUp = true;
13.             }
14.             if (Input.GetKeyUp(KeyCode.Space))
15.             {
16.                 goingUp = false;
17.             }
18.  
19.             if (Input.GetKeyDown(KeyCode.C))
20.             {
21.                 goingDown = true;
22.             }
23.             if (Input.GetKeyUp(KeyCode.C))
24.             {
25.                 goingDown = false;
26.             }
27.  
28.             Vector3 move = Cam.right * horizontal + Cam.forward * vertical + Cam.forward * vertical;
29.  
30.             if (goingUp && !goingDown)
31.             {
32.                //make the player go up along the global y axis
33.             }
34.  
35.             if (goingDown && !goingUp)
36.             {
37.                 //make the player go down along the global y axis
38.             }
39.             if (!goingDown && !goingUp)
40.             {
41.                 move = Cam.right * horizontal + Cam.forward * vertical + Cam.forward * vertical;
42.             }      
43.  
44.             Cam.Rotate(-mouseY, 0, 0);
45.            
46.             transform.Rotate(0, mouseX, 0);          
47.  
48.             rb.velocity = new Vector3(move.x * SwimSpeed, move.y * SwimSpeed, move.z * sideSwimSpeed);
49. }
50.  

 

I came up with the solution myself, feeling kinda dumb now.

Code (CSharp):

1. if (goingUp && !goingDown)
2.             {
3.                 rb.AddForce(0, 100, 0);              
4.             }
5.  
6.             if (goingDown && !goingUp)
7.             {
8.                 rb.AddForce(0, -100, 0);              
9.             }