Fish Animation

Hello All,
I have a little problem animating fish.
I have created an armiture and have created vertex groups for the movment of the body and fins, of which works fine.
The problem is when I try to add soft body to the fins to make them move fluidly the body of the fish falls off the bones and/or as I have created soft body groups and weight paint them individualy they effect the rest of the mesh.
I have also tried this by keeping the fins seperate from the body and creating the soft body groups, and that does fine by its self but the animation messes up and makes the tail fins separate from the body.
Any help would be greatly appreciated,