A woman has died following a water incident at the Rakaia River mouth this afternoon.

Emergency services responded to the south side of the river mouth at around 1pm after reports that a group had become stuck in the water while attempting to cross on quad bikes.

A witness told Chris Lynch Media she watched the quad bike get struck trying to head back home during high tide.

“We were there fishing at the river mouth as it all unfolded, it was a horrible event to witness”, she said.

Fire and Emergency New Zealand, Police, and St John attended the scene, with assistance from a member of the public using a private vessel.

Six people were recovered from the water.

One person was found dead, while another was airlifted to Christchurch Hospital in critical condition by the Westpac Rescue Helicopter.

Police are continuing to investigate the incident.