A man was stabbed on a fishing vessel berthed in Nelson in the early hours of this morning.
The victim was a crew member and was taken to Nelson Hospital with serious injuries.
He is currently undergoing surgery for his wounds, a police spokeswoman said.
The stabbing occurred at 3.30am.
A 30-year-old fellow crew member has been arrested and will likely appear in the Nelson District Court this afternoon.
The charges he will face are yet to be confirmed.
Police are not seeking anyone else in relation to the matter.