The concavity has {HEAD ~ a longitudinal axis} of {TAIL ~ symmetry} coincident with a longitudinal axis of symmetry of the watercraft 
of
The concavity has { HEAD ~ a longitudinal axis } of { TAIL ~ symmetry } coincident with a longitudinal axis of symmetry of the watercraft
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH