A neighbour of Sydney seaplane crash victim Richard Cousins has revealed the multimillionaire CEO sent out invitations to his upcoming wedding in the days before his death.

Mr Cousins, 58, was due to wed Emma Bowden, 48, on July 21 and an engagement party was planned for early March.

A neighbour who lives in Hyde Heath, near Mr Cousins' Buckinghamshire home, told the Mirror that his friend "was so looking forward to the wedding".

Emma Bowden was engaged to Richard Cousins.

Richard Cousins is the CEO of catering giant Compass. (Youtube)

"I knew from him that (Mr Cousins' first wife Caroline) always said that if he found someone else she would want him to be happy and he was so happy. He was the happiest he had been in a long while," the man, who asked not to be named, said.

Mr Cousins' first wife, Caroline, died in 2015 after being diagnosed with cancer six months earlier.

The former boss of Sydney seaplane crash victim Emma Bowden has described the 48-year-old as a "wonderful" presence, comparing her to American actress "Grace Kelly".

Lisa Byrne, ex-editor-in-chief of OK! Magazine, where Ms Bowden was arts editor, said her colleague was "serene" and "regal", and would keep a calm head whenever there were late changes to the publication just before it went to press.

Emma Bowden and her daughter Heather Bowden-Page were on holidays with their new family.

Heather Bowden-Page in a picture taken by her mother. (Image: Facebook)

Mrs Byrne compared Ms Bowden to the American actress known for her elegance and style.

"She quite regal, very serene, and very well educated, we used to have great chats, " she said.

"I used to call her the Grace Kelly of the office because she had a great aura about her.

"Nothing ever phased her. We had to change pages at the last minute – things were being altered, features being dropped and pages redrawn – and she was always willing to put in the extra hours.

"She was such a wonderful, calming influence in the office, and I never heard her grumble."

William Cousins, 25, died alongside his brother and father in the crash. (9NEWS)

Edward Cousins, 23, was planning on joining the police force after finishing university. (9NEWS)

Sea plane pilot Gareth Morgan perished in the crash. (Supplied)

Ms Bowden was killed alongside her 11-year-old daughter Heather Bowden-Page, her fiancé Richard Cousins, and his adult sons William Cousins, 25, and Edward Cousins, 23, on New Year's Eve when the joy flight they were on crashed into the Hawkesbury River.

Sea plane pilot Gareth Morgan, 44, also died after the Sydney Seaplanes charter crashed into the river near Cowan Creek, 40km north of Sydney's CBD.

Detective Superintendent Mark Hutchings from the NSW Police Marine Area Command described the incident as “nothing more than just tragic” and said formal identification by the Coroner is still ongoing.

"We can confirm that the persons involved in this matter, along with the pilot, were visitors from overseas," Detective Superintendent Mark Hutchings said.

Richard Cousins was the chief executive of global catering giant Compass and was holidaying in Sydney with family when their trip was tragically cut short.

"We are deeply shocked and saddened by this terrible news. The thoughts of everyone at Compass are with Richard’s family and friends, and we extend our deepest sympathies to them," Compass Group chairman Paul Walsh said.

"It has been a great privilege to know Richard personally and to work with him for the last few years. Richard was known and respected for his great humanity and a no-nonsense style that transformed Compass into one of Britain’s leading companies."

He lost his first wife, Caroline, to cancer in 2015.

Cousins was due to step down from his position in March after announcing his departure from the company in September, after having been named number 11 on the 2017 100 Best Performing CEOs in the World by the Harvard Business Review.

Cousins' son Will was head of press for political campaigners Open Britain and was described by the group's chairman Roland Rudd as an "extraordinary young man" who would be "missed beyond words".

Tributes have already begun to flow online.

Neighbours at the family home in south-west London described how "distraught" relatives were seen entering the property on Sunday after hearing the news.

Lata Maisuria, a neighbour who has lived in the area for over 30 years, said the holidaymakers were a "happy-go-lucky" family and that neighbours would be shocked by their death.

She said Heather had recently started at a local secondary school.

"She seemed happy there," Ms Maisuria said.

"I asked the daughter a couple of times how she was liking it, and she seems to have fitted in nicely at the school, and she seemed to be very happy."

"She really wanted to go to that school, she was looking forward to it."

Mr Morgan, originally from Canada, had previously described his love of flying in a video uploaded to YouTube by Sydney Seaplanes.

Pippa Middleton chartered a Sydney Seaplanes flight during her Australian honeymoon in May 2017. (Image: AAP)

"My dad’s friend back in Vancouver owned a plane and he took me up a couple of times, kind of got me hooked," he said.

"That was in my early 20s... I thought this looks like a great career."

He previously worked with a company in British Columbia that flew people on fishing trips, often in harsh conditions.

The wreckage of the plane is still submerged under 13 metres of water and is slowly being recovered.

Police are currently working on refloating the wreckage, which is necessary for forensic air-crash investigators to piece together what went wrong.

The Australian Transport Safety Bureau is working with police to investigate the incident.

Sydney Seaplanes managing director Aaron Shaw said the company was "deeply shocked" by the tragic accident and Mr Morgan was "deeply respected".

Divers recover parts of the sea plane and a body are recovered from the Hawkersbury River. (Image: AAP)

"All at Sydney Seaplanes are deeply shocked by this incident and the resulting loss of life," he said.

"We wish to pass on our heartfelt condolences to the Bowden and Cousins families, and the family of our pilot Gareth Morgan, who were tragically killed."

Mr Morgan worked for Sydney Seaplanes over two periods. He was first employed by the company from 2011 until 2014, leaving to fly seaplanes in the Maldives. He then returned in in May 2017.

Mr Shaw described him as an "extremely experienced pilot with over 10,000 hours flying time, of which 9000 hours were in seaplanes".

Mr Morgan has been described as an experienced seaplane pilot. (Supplied)

He said Mr Morgan would have flown the route he did yesterday "hundreds of times".

"We're just going to be working with the authorities, we're going to dedicate all our resources to doing so," Mr Shaw said.