She said the motorcycle's exhaust pipe had left her partner with burns that required plastic surgery.
"Apart from that, he broke his collarbone but there were no head injuries. He recovered really well and we were actually home in time for the rugby on Sunday night."
She said if her partner had not been knocked out, the accident would likely have been minor.
"On any other day, he would have just got up and picked his bike off him and continued on. It's a shame because he had had his helmet on all day."
An off-duty emergency department nurse helped to treat the man at the scene before paramedics arrived in the Westpac Rescue Helicopter, which landed on the beach beside the patient.
He was then flown to the Wellington Hospital emergency department.
The man's partner said no-one was certain how the accident had occurred, as there were no logs or other obvious obstacles on the beach near the crash site.
Riversdale Surf Life Saving Club captain Mike Taylor said vehicles were "very common" on the beach, but must be driven away from the houses to either the northern or southern ends of the town.