WITHOUT a cloud in the sky on a crisp winter morning, the conditions were prime for experienced jumper Tim Fitzsimmons and his pilot.

The pair loaded up the plane at Sydney Skydive's headquarters in Wilton and, shortly after 8.30am, headed skyward.

The 27-year-old Raby man had more than 1000 jumps under his belt.

Colleagues said he was not a risk-taker and safety was paramount. But something went wrong as Mr Fitzsimmons neared the ground after jumping from almost 5000ft.

Mr Fitzsimmons, a staff member at the skydive centre, slammed into the ground at high speed, causing multiple broken bones and serious internal injuries.

"The man was performing a swooping canopy manoeuvre, where he's collided heavily with the ground," a NSW Police spokesman said of Tuesday's accident.

Mr Fitzsimmons underwent emergency surgery at Liverpool Hospital but died that night.

His heartbroken girlfriend Leah Drake yesterday wrote on Facebook of her pain at losing her "soul mate".

"My heart is shattered to a billion pieces, words cannot describe the pain I am in, and only you could take it away baby," Ms Drake wrote.

"I will miss everything about you, your gorgeous face, your infectious laugh . . . the way you loved your family, friends and me."

She said Mr Fitzsimmons' family took solace knowing he died doing something he loved so much, and that he could now "keep ying".

"Fly free bub. I will love you forever, visit me in my dreams," she wrote.

Swooping involves jumping out of a plane with a canopy parachute, before rotating or turning to be able to skim across the ground or water.

But Sydney Skydive services manager Russell Brown said Mr Fitzsimmons might have been doing a "hook turn" -- not swooping.

"It was just a normal jump but basically he turned too close to the ground," Mr Brown said.

Police returned to the skydive centre yesterday to carry out an investigation into Mr Fitzsimmons' death but said it was being treated as an accident.

Skydiving blogs were abuzz with people discussing whether swooping was too dangerous.

In February, a skydiver who had completed more than 8000 jumps and trained US Navy SEALs died after "swooping" in a competition in California. Sean Carey, 35, hit a pond at high speed and died later in hospital.

Tim Fitzsimmons, from Raby, died early this Wednesday after more than 12 hours of surgery at Liverpool Hospital.

He suffered serious internal bleeding along with chest, abdominal and leg injuries following his failed jump at 9.30am yesterday. Paramedics rushed to the Sydney Skydiving Centre at Wilton, in the city's southwest, transporting the experienced BASE jumper and skydiver by helicopter to hospital.

Mr Fitzsimmons heartbroken girlfriend Leah Drake posted on Facebook her sorrow at the tragic accident.

“My heart is shattered to a billion pieces, words cannot describe the pain I am in,” Ms Drake said.

“My soul mate, my best friend and lover. I know you are in a better place now one with only the happiness and peace that rests in your soul.”

“I will miss everything about you, your gorgeous faceests in your soul. I will miss everything about you, your gorgeous face, your infectious laugh, your ability to make anyone smile and the way you loved your friends, family and me.

"My world will be a lonely one without you but I know you will take away my darkness. Fly free bub. I will love you forever visit me in my dreams."

It is believed Mr Fitzsimmons was swooping at the time, a technique where the jumper dives at high speed before using their parachute to pull out of the plunge a short distance above the ground.

"R.I.P big bro. I love you," his sister Nikki Fitzsimmons said on his Facebook page last night.

Police will investigate the death and will seize the parachute, interview witnesses and examine any video footage of the incident.

Friends flooded social media with messages of support for the family of the well-respected skydiver.