Police are continuing the scene examination today.
Yesterday, Tasman District crime manager Detective Inspector Paul Borrell briefed media near the site of the incident.
"The death is being treated as suspicious but we are yet to establish if this is a homicide," he said.
"We are examining three boats moored in the area gathering any evidence that will assist this investigation to piece together what has actually occurred and has led to this man's death. It is expected that this will take several days."
The boats are located opposite Neale Park playing fields.
Police say anyone who saw people in the area on Wednesday afternoon or Thursday morning can call 03 546 3895 or Crimestoppers on 0800 555 111.
- nzherald.co.nz with Nelson Live