Traffic is backing up after a car crashed into a barrier and went into the harbour from State Highway 29A just north of the Maungatapu Bridge.
A St John Ambulance spokeswoman said a man had been taken to Tauranga Hospital in a serious condition after the crash.
Police were called to the crash between Truman Lane and the Maungatapu Bridge just before 3pm today.
A police spokeswoman said earlier a single car in the southbound lane had crashed through a barrier and gone down a bank into the water.
She said emergency services were working to get the person up the bank to receive medical attention.
A helicopter was on standby to help remove the car from the shallow water.
A reporter at the scene said the crash was just north of the Maungatapu Bridge. There were multiple fire, police and ambulance vehicles on the scene.
City-bound traffic was backing up at the Baypark roundabout. Traffic was moving slowly past the scene, which was just after the two lanes merged into one.
An area of bank has been taped off and firefighters have been seen preparing to absail down the bank.
A St John ambulance said one ambulance crew and manager were on scene.
A Fire and Emergency New Zealand spokesman said it was called to the crash around 3pm.