It took two hours for the Ruahihi Canal to be drained enough before the body of a Downer employee could be brought back to land.
Emergency services worked past sunset to recover the body after being called to the canal off McLaren Falls Rd in Omanawa about 1.20pm on Wednesdayafter reports of a vehicle going into the water.
The windy road and canal were separated by a steep paddock, and the truck went through three fences before being submerged right-side-up in the canal.
A Downer spokeswoman confirmed the person inside the truck was a Downer employee from the Tauranga team.
"This is a tragic event and we are working with the family and the local team to support them through this challenging time."
A Trustpower spokesman said the lowering of the water level took about two hours, at about 100mm per 15 minutes, and was done so the vehicle could be accessed safely.
The company was contacted by police and immediately sent a staff member from Ruahihi Power Station to assist them, the spokesman said.
The Ruahihi Canal carries water from Lake McLaren to the Ruahihi Power Station, and the only way to lower the water is to run it out through the power station.
Once the police requested the lowering of the water level, the company ran the power station at maximum capacity to drain the canal as quickly as possible, he said.
"We continued this until the generators tripped out, which meant the canal was at the lowest level it can get to."
The gates between Lake McLaren and the canal will remain closed until the vehicle is recovered to prevent any further water entering the canal.
The water level will be raised once the vehicle is recovered, using water stored in Lake McLaren.
Trustpower worked with the Bay of Plenty Regional Council to place booms across the canal downstream of the incident, to mitigate any potential oil leakage from the vehicle.
Mount Maunganui Surf Lifesaving was called by police to use the club's inflatable rescue boat.
Senior lifeguard Kent Jarman said he was there to assist police by providing the boat and advice on using it, and the mission was continued by police.
Jarman said it was fortunate the water in the canal, which was six metres deep, was able to be lowered enough for police to access the truck with the boat.
The body was brought to land by police, and Jarman said they had left the scene by 7pm.
Today, the boat and all equipment used will be blessed by local iwi before it is used again, something which was standard protocol after carrying the body of a deceased person.
Carlo Ellis, manager of strategic Māori engagement at the council, blessed the raft.
In his 40 years at the Mount Maunganui club, this was the first recovery operation he had been to which involved a vehicle submerged underwater.
The retrieval operation took about three hours as the vehicle was completely submerged in the canal.
A police media spokeswoman said the vehicle was recovered this afternoon.