The skipper of a Department of Conservation boat that collided with a private yacht in the Marlborough Sounds was knocked unconscious in the crash.
Police say the collision happened in the Bay of Many Coves in Queen Charlotte Sound at about 10am on Wednesday.
They say the skipper's memory about what happened is shaky as a result of him being knocked out.
He is in Wairau Hospital in Blenheim, where he is in a stable condition.
The sole crew member on the yacht was treated for hypothermia.
Police say it is fortunate the yacht became tangled in the DoC boat, which stopped it from sinking to the bottom.
It has been retrieved and taken to Picton alongside a barge.
While police have spoken with both skippers, the investigation into the collision will be conducted by Maritime New Zealand and the Harbourmaster.
Marlborough Harbourmaster Alex van Wijngaarden says the yacht skipper will be spoken to on Thursday.