First, how to tell if it's dead? It will be all black and not moving. the legs will not be pointed upward like normal. And the legs will be limp and easily movable (unless the individual has been dead for a while) now, symptoms (before death) including. Unitentinaly flipping on back and unable to right its self. Lack of wax or like in photo it had black spots that then spread around the body till death. Thy are also much less active, sometimes this can mimic the swimming motion, but most of the time it's more random leg movements and not forward and back like in concussion symptoms. Also thy only seem to have the ability to move forward this varies from Individuals to individuals, but is the case for most. Remember there is no scientific study's supporting this. This is based on research and personal experience.