He had tried to get back to the raft, which was only one of two metres away, by jumping back into the river. Instead he had passed under the raft and was last seen floating down stream in the deliberate body position to negotiate rapids; on his back, facing downstream, his arms folded in front of his chest and his legs tucked up ready to push off any obstacle the river pushed him towards.
The crew were not able to find Mr Mason and immediately paddled out to raise the alarm.
Mr Foster said river conditions at the time were about 650cu m per second, about four times the normal run.
Mr Mason's body was found on October 16, about 10km downstream from the rapids.
Dr Bain asked Mr Foster if it was correct Mr Mason had re-entered the water.
Mr Foster confirmed it was and said it was a tragedy Mr Mason had not taken the time to walk 100m to a beach area where the raft could have come ashore.
A pathologist found Mr Mason's death was consistent with fresh-water drowning. Dr Bain said it had been an unfortunate decision on Mr Mason's part to go back into the water.
"If you get chucked out of a raft and end up on a bank, stay there," Dr Bain said.