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