Police have named the man whose body was found by boaties at the entrance to Wellington Harbour on Monday.
He was Graham Hutcheon, aged 57, from Upper Hutt.
Police said they have seized and would be searching a vehicle belonging to the man which they found near Wellington's ferry terminal.
Meanwhile a post mortem examination is being completed and the final results are yet to come, police said.
Detective Senior Sergeant Mike Sears said police and the Interislander were still trying to determine whether Hutcheon was a passenger on the 8pm Cook Strait crossing sailing on Sunday.
- The Dominion Post
Is New Zealand's airport security stringent enough?Related story: Risky objects bypass Wellington Airport security