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