THE hunt for the first shot fired in World War I has moved a step closer with maritime explorers seeking to use powerful sonar equipment to scan the bottom of Port Phillip Bay.

Southern Ocean Exploration is seeking to source a $130,000 magnetometer - which is used by the US Navy to clear unexploded Japanese ordnance in Pearl Harbor - to hunt for the first shell fired in the Great War.

The 40kg solid steel shell was fired from the Point Nepean fort at the German ship SS Pfalz within two hours of war being declared by Britain on August 5, 1914.

The State Government has backed the plan to find the shell - the first Allied shot fired anywhere in the world in World War I - as a part of centenary commemorations.

“If we get the money raised and get the right equipment we will find the shell,” Southern Ocean Exploration founder Mark Ryan said.

Mr Ryan said assessments of records from the time indicate the shell would lie on the bay floor at a depth of up to 30 metres, south of Pope’s Eye.

But he believed it would now be covered by sand and the hi-tech magnetometer would be required to find it.

“Finding the first shot fired by the Allies in the first World War would be international news,” he said.

Aqua Power Marine have donated a new 22 foot vessel to tow the magnetometer in the search which is hoped to be underway by the centenary in August.

“The equipment the US uses can find a .22 (bullet) under feet of sand. We are pretty confident,” filmmaker Terry Cantwell, of Whitewater Documentaries, said.

Practice rounds were not known to be fired into that area of Port Phillip Bay and due to the size of the solid shell - 150mm diameter by 600mm length and its probable position in a seabed dune trough, it is not believed to have shifted far by tidal movement, Mr Cantwell said.

Victorian Anzac Centenary Committee chair Ted Baillieu said the government was planning an event to commemorate the “first shot”, and finding the shell would be a coup.

“The VACC has already raised for consideration the possible location and recovery effort of that first shell, if intact,” he said.

“If it was possible, such a find would, of course, be of worldwide significance.”

Based on records of the position of the Pfalz and the expected shot trajectory, the search area has been refined to about 30 square kilometres.

Business and public donations to help fund the magnetometer purchase can be made through the IndieGoGo website.