Hamilton man George Charles Taiaroa, 67, was shot while manning a stop-go sign on Tuesday afternoon.
The shooting happened near Tokoroa on Tram Rd, a short stretch of rural road in the Kinleith Forest area which bridges the Waikato River.
The dive squad will be searching the site for most of the day, a police spokeswoman said.
"The dive search is part of the scene examination process looking for anything that might assist the investigation," she said.
She would not confirm if the team was looking for a weapon in the river.
Police investigating the shooting of Mr Taiaroa said they were encouraged by the positive response from the community.
Several other people at the scene saw what looked like a blue Jeep Cherokee speeding off towards Tirohanga Rd.
Dozens of calls had been made to the investigation team and there was a regular and steady flow of information, particularly around sightings of the vehicle.
Detective Inspector Mark Loper said earlier a vehicle was stopped, before the shooting, to let a truck cross over the bridge on Tram Rd.
"Once that truck cleared the bridge, a 4x4 motor vehicle drove off from where it had been stopped near the victim.
"As it did so the victim was seen to fall to the ground," Mr Loper said.
Mr Taiaroa's body was removed from the area on Wednesday morning and was yesterday taken to Auckland for a post-mortem examination, which confirmed he was fatally shot.
Detective Inspector Tim Anderson said it was still too early in the investigation to speculate about motives.
No one had been arrested at this stage.
"Currently we have over 30 experienced staff assisting with completing area inquiries."
Mr Anderson said he believed the homicide was an isolated incident.
Anyone with information should contact Taupo police on (07) 378 6060, or anonymously contact Crimestoppers on 0800 555111.
