A councillor says a fatal quad bike incident at the Rakaia River was a tragedy - and could've been much worse

A woman died near the rivermouth in mid-Canterbury on Saturday, and six others were injured - one critically.

Ashburton Councillor Russell Ellis was there earlier in the day - and came back because of the sea conditions.

He says the group was about four kilometres down the beach from the rivermouth.

Ellis says high seas coming through the low area caught them out - and others.