如何创造圆形物体进入和分离厚物的效果

Based on the image below (I used different colours for circle and flat surface so they can be seen, but in the end the colours will be the same), using Swift and Spritekit, I am trying to create the effect of a circular object entering a thick substance (not necessarily sticky) and separating from the thick substance. Basically, when the circular object is separating, it will pull away from the flat surface as it forms into a circle. I wanted to use image animation frames, but since the objects are SKSpriteNodes with physics bodies this will make timing the collision of objects with animation quite difficult. Another approach would be using CAAnimation, but I don't know how this can be combined with SKSpriteNodes with physics bodies. How can I create this separation effect using any of the above stated approaches or a different one?Based on the image below (I used different colo