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