Ngatai Lynette Manning, also known as Mallory, was found by a kayaker near Dallington Terrace, east of the city centre, about 6.50am on Friday.
She suffered extensive injuries and was believed to have been dead before entering the water.
Police have confirmed they are looking for two weapons.
Detective Inspector Greg Williams told Radio New Zealand another client who was with Ms Manning before she was murdered had come forward to police.
This had helped narrow down the time of the attack. Ms Manning was with that client until around 10.20pm and was picked up by the next client at around 10.35pm, he said.
The person who picked her up at that time had not come forward to police, said Mr Williams.
The last text message Ms Manning sent was at 10.43pm.
Her watch had stopped about 10.59.
Police were appealing for any sightings of someone who was out driving in the area at the time.
The person was possibly parked and waiting for the right opportunity before they picked up Ms Manning, said Mr Williams.
A lot of people were moving in the area at the time and anyone who saw anything suspicious should come forward.
Mr Williams said the response from the public had been "fabulous".
Police had a "fairly good idea" of what weapons were used to kill Ms Manning.
She was last seen wearing a blue bikini top with dots and a short red skirt and black ankle length boots or black high heeled shoes with two straps.
Ms Manning's brother, Robin Manning, said he was close to his sister and last saw her six weeks ago.
"She was actually a really caring, down-to-earth person who just had a demon on her back and couldn't shake it off, but she did try numerous times."
Mr Manning said his other sister died earlier this year and he was now focused on supporting his mother.
