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