A New Zealand kayaker received a rude shock when a seal slapped him in the face with an octopus, in a video which was posted on Instagram on Monday (Sept 24).

Mr Kyle Mulinder had been paddling off the South Island town of Kaikoura over the weekend with a group of friends.

The group was testing out new GoPro Hero7 equipment at the time and caught the entire incident on camera.

Mr Mulinder said he saw the two animals thrashing about for a while but unexpectedly became part of the action.

"I was like, 'Mate, what just happened?' It was weird because it happened so fast but I could feel all the hard parts of the octopus on my face," Mr Mulinder told 7News.

His friend, film-maker Taiyo Masuda, said it was an incredible, "raw moment".

Mr Masuda, 23, added: "We were just trying to film cute seals but it ended up being very brutal. We instantly just laughed so hard."

GoPro posted the now-viral video on its Facebook page on Tuesday (Sept 25), asking users to caption the moment for an opportunity to win a GoPro Hero7.

Political commentator Kelly Cohen tweeted the video, with a caption that implied the surprising, wet slap reminded her of the unforgiving news cycle.

"I'm the kayaker, the octopus is the news cycle," she tweeted.

The seal was likely trying to rip off the octopus' tentacle with the force of the throw as part of its lunch.

However, the octopus emerged as the victor - it climbed and held on to the bottom of Mr Mulinder's kayak, while the disgruntled seal swam off.