When {HEAD ~ the chamber} is filled with {TAIL ~ sufficient air}, the rearward section becomes buoyant and pivots to its floating position 
is filled with
When { HEAD ~ the chamber } is filled with { TAIL ~ sufficient air } , the rearward section becomes buoyant and pivots to its floating position
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH