A pilot and five skydivers have been rescued following a light plane crash in south-east Victoria, Australia.

The pilot, a man in his 50s, was trapped for almost two hours after the plane went down about 2.20pm AEDT near Tooradin Airfield, an Ambulance Victoria spokesman said.

In a complex rescue effort involving more than 20 paramedics, police, the CFA and SES, rescuers had to dodge snakes and walk through mud, mangroves and water sometimes waist-deep to reach the plane, which came down in mud flats beside a river leading to Western Port Bay.

The pilot was treated in the cabin before crews freed him and he was flown to The Alfred Hospital with leg fractures and in a serious condition.

A male passenger, 29, was also flown to the Royal Melbourne Hospital in a stable condition for a possible fractured hip.

Another four passengers suffered minor injuries, some with chemical burns from the plane's aviation fuel; all were taken to hospital in a stable condition.

Intensive care paramedic David Llewelyn said it was a difficult scene.

"We had to trek in about a kilometre with all of the equipment and cross over several tributaries to get to the plane," he said.

"Rescuers spotted three tiger snakes on the way in."

Mr Llewelyn said the plane had landed on its belly in waist-deep mud.

"Those who went into the water to assist the injured were caked in sticky mud and also ended up suffering petrol burns from the aviation fuel," he said.

An SES boat rescued those from the plane and ferried rescuers to and from the crash site.

A police helicopter was also used to winch some of the rescuers out of the water.

Twenty one rescuers had to be decontaminated because they were in the water and aviation fuel for some time.

Some suffered mild hypothermia from spending several hours in the water at the crash site.

Two were taken to hospital with hypothermia and chemical burns from the aviation fuel.