Rotate Sprite Based on Speed & Direction of movement

Hi,
I'm hoping that someone can point me towards a solution/tutorial (not 100% code as I like to have a guide but work it out myself from that) on how to have my character rotate to more accurately reflect the movement. What I have is:

• 2D side scroller with whales/dolphins in it that dive under the water & jump out of the water.

What I'm trying to do:

• have them slowly rotate facing up when jumping up (Gradually steeper as they go higher)
• have them slowly rotate to level as they reach the top of their arc
• slowly rotate facing down as they fall back towards the water (Gradually steeper as they fall further)
• continuation of both if they are jumping out of the water from starting below the surface to build up speed or diving further down after jumping out of the water
• Sort of like a Sin curve.

I already have the actually movement working how I want, I just want to get the sprite rotating to help convey the movement. I've tried linking rotate to velocity but it's not quite right & looks really weird with incomplete turns.

I've attached a (bad) image to try & show what I mean. Also the code I had tried that sort of worked best but still looked wrong.

Code (CSharp):

1. // change fish angle dfacing up & down depending on direction of movement
2. //        Vector2 dir = transform.GetComponent<Rigidbody2D>().velocity;
3. //        float angle = Mathf.Atan2(dir.y, dir.x) * Mathf.Rad2Deg *Time.deltaTime * 15;
4. //        transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);

Thanks

 

something like this might help...

http://answers.unity3d.com/questions/14899/realistic-rotation-of-flying-arrow.html

 

Thanks, will check it out