Loren Dougan, who was Ms Bain's riding companion on the day she died, said she and Ms Bain had coffee at her home before setting off.
The two had had ridden along a stopbank before following a track to the Ruamahanga River where Mrs Dougan had crossed several times, although Ms Bain, an experienced endurance rider, never had.
"Once we were at the river, I could see it was discoloured and a bit high but I was not concerned about getting across," Mrs Dougan said.
The plan had been to cross from near Rathkeale College on the western side to Blackrock Road on the east.
Mrs Dougan said the pair rode their horses into the water to see how deep it was, with herself on the upstream side and Ms Bain a metre to her right and downstream.
She could remember her feet and stirrups were above water as they rode into the river.
Ms Bain had commented that she was "not comfortable" with the situation and had tried to turn around her horse.
It was then the horse panicked, reared and lost its footing.
Ms Bain was tossed from the saddle but had at first managed to hold on to the saddle and reins as her horse tried to regain its feet.
Mrs Dougan said Ms Bain and the horse had been swept downstream "over the lip" into swifter, deeper water and although the horse had struggled out of the river, its rider was swept into willows as she screamed for help.
Her body was found washed up on the tip of an island in the river. Clint Dougan, who had arrived on the scene, waded into the river and administered CPR.
In answer to a question from Masterton police detective sergeant Bill van Woerkom, Mrs Dougan said Ms Bain had been wearing a safety helmet.
Expert witness John Stevenson, of Reporoa, an elite coach for New Zealand Endurance Riding, gave evidence on the behaviour of horses when crossing rivers.
He said it was possible when Ms Bain tried to turn her mount downstream that the horse's tail had washed under its back legs, causing the animal to think it was a branch or some other obstruction in the river.
"'I personally would not turn a horse in water but if I did, it would be upstream," Mr Stevenson said.
Summing up before reserving his finding, the coroner said Helen Bain had died doing what she loved.
"She was a capable horsewoman who made a decision to cross the river before deciding to turn her horse around when she became a bit concerned."
Referring to the horse losing its footing in the dirty river, Mr Smith said he knew from his own experience crossing rivers, although not on horseback, that there was nothing more frightening.
He said Ms Bain was not a swimmer - although her father Peter Bain had said his daughter could swim but not well - and things had happened so quickly she probably didn't have much chance.
