The concavity has {HEAD ~ a trailing end} coincident with {TAIL ~ the transom} or trailing edge of the watercraft and has a leading end disposed forwardly of the transom 
coincident with
The concavity has { HEAD ~ a trailing end } coincident with { TAIL ~ the transom } or trailing edge of the watercraft and has a leading end disposed forwardly of the transom
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH