Setting a jump force on a rigidbody

Hello people, I'm very new in unity so any help will be really appreciated.

I'm making a game about a fish jumping out of the water and doing tricks (like dolphin Olympics).

My player is a game object with a rigidbody, and the water is a plane . when the player is on the water the rigidbody is set to IsKninematic and I move and rotate the player with transform.Translate and transform.rotate , when i get out of the water i use this

 void Update () 
     {
         rigidbody.isKinematic = m_bIsKinematic;
         
         
         //Amount to move
         float amtToMove = playerVelocity *        Time.deltaTime;
         
         // player Movement
         transform.Translate (Vector3.right * amtToMove);
         
 
         
         //rotation
         if (Input.GetKey(KeyCode.Z))
             transform.Rotate(0,0,-rotateSpeed);
         
             if (Input.GetKey(KeyCode.X))
                 transform.Rotate(0,0,rotateSpeed);  
             
         
     }

 void OnTriggerExit(Collider Otherobject) 
     {
              if (Otherobject.tag == "Sea")
             {
             bMove = false;
             collider.attachedRigidbody.useGravity = true;
             
                     //a bool to enable or disable IsKinematic
                     m_bIsKinematic = false ;


             playerVelocity = 0;
             
             }
     }

So when the player gets out it turn off the IsKinematic and the UseGravity is set to Enable and turn to 0 the player velocity .

SO here is the problem . I want to keep the momentum and velocity of my player to perform the tricks but as i set the player velocity to 0 it stop movement immediately. If i left the player velocity running it jumps out and the gravity pull me down but i can move in the jump like I'm still swimming (not like it should be).

Is there a function or a method or to keep my momentum and velocity but controlated by the physics? I just want to move the fish like a truly kumping dolphin. Any help , workaround , comment will be really apreciated. Thanks for your help.