A woman has died after a quad bike became stuck in the incoming tide at the Rakaia River mouth on Saturday afternoon, triggering a frantic rescue effort.

Emergency services responded to the south side of the river mouth at around 1pm Saturday afternoon, following reports that a group of six people had become stranded in the water while attempting to cross on quad bikes.

A local resident who witnessed the incident said they saw the quad bike become trapped as the tide rushed in.

“More and more water came in, and the quad bike was badly stuck. It was very dangerous for all involved. The waves were very, very big, which just carried on crashing in,” they told Chris Lynch Media

Another witness described the dramatic rescue efforts, which unfolded near the Rakaia Huts.

“It was a full-scale operation down by Rakaia Huts. The rescue helicopter arrived about an hour to an hour and a half after it started,” they said.

“I watched a side-by-side vehicle get struck while trying to head back home during high tide. Very sad to see.”

The witness urged people to take extra care this summer, saying, “I think this is a timely reminder to be safe. If it isn’t safe to do it, don’t do it.”

Another person who has fished at the river mouth before said the conditions there can change quickly.

“I’ve almost been swept away there fishing once, and when the waves start coming over the bar, you can’t even see them coming,” they said.

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

Police are continuing to investigate the incident.