Police identified the body as that of a 52-year-old fisherman from Dunedin. The death is not being treated as suspicious.
It is one of four sudden deaths around the West Coast at the weekend -- all referred to the coroner.
A 69-year-old Nelson Creek resident died on Friday night, a 91-year-old woman was found dead at Hector, and a 67-year-old man died at Inchbonnie on Sunday.
On Saturday, a group taking advantage of the settled weather set out in their boat about midday on a family adventure with the children, over the Grey River bar.
About 15 minutes later they had pulled in just north of the Point Elizabeth Walkway for a closer look and were enjoying the sight of a pod of about a dozen dolphins leaping about near the boat about 200m offshore, when they spotted the body of a man floating in the eddy.
"There's a lot of cool rocks out there and we were checking those out ... and enjoying the calm sunny weather," the woman said.
The witness said she just happened to look over the side and noticed the body. They called emergency services and stood by for about an hour watching the body drift until Kotuku Surf Rescue arrived from Rapahoe to retrieve the body.
The boating party went on their way up the Coast before returning later in the afternoon, and in another fluke spotted a quad bike floating in the sea off Rapahoe. It was later confirmed as belonging to the dead man.
The boatie said it was a fluke they had pulled into the area where the bike was floating. Obviously in the circumstances it was fortuitous as the man's family would be at least grateful to have his body back, and it possibly saved an extended official search, the woman said.
Senior sergeant Mark Rowbottom, of Greymouth police, said how the man came to be in the sea and where he had been was still being investigated, but there was no evidence to suggest anything sinister in his death.
"We don't know exactly how he got in there ... there was a quad bike located that was his. He was a keen fisherman," Mr Rowbottom said.
Police inquiries included whether the dead man had been living permanently or just staying in the area.
Meanwhile, the Ngahere Volunteer Fire Brigade and the NZCC West Coast Rescue Helicopter were dispatched early on Friday evening to tend to a 69-year-old Nelson Creek man who had suffered a medical event on Callaghans Ridge, about 20 minutes' walk up the track from the Nelson Creek swingbridge.
Fire chief Tommy Daly said they attempted to find a landing zone for the helicopter, which eventually winched a paramedic to the ground in poor light, about 5pm.
The patient was eventually lifted out by the helicopter and flown to Grey Base Hospital but later died.
Mr Daly paid tribute to the "extraordinary skill" of the helicopter staff who in difficult circumstances were able to get their paramedic down to help at the scene.
Police were also called to a house in Hector at the weekend after a neighbour checking found a 91-year-old woman dead in her home.
On Sunday morning about 11.10am the rescue helicopter was called to Inchbonnie after a 67-year-old man suffered a medical event.
Helicopter staff including an intensive care paramedic were on the ground for about two hours trying to assist the man, who died at the scene.
- Brendon McMahon