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