{HEAD ~ The collar} includes {TAIL ~ a buoyant forward section} and a controllably buoyant rearward section pivotally connected to the rearward section for pivotal movement between a horizontal floating position and a sunken position 
{ HEAD ~ The collar } includes { TAIL ~ a buoyant forward section } and a controllably buoyant rearward section pivotally connected to the rearward section for pivotal movement between a horizontal floating position and a sunken position
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH