TWO divers polishing and taking underwater photographs of a tanker's propeller were startled when it suddenly roared to life last August.

The rotation of the propeller blades left one of them, Mr Abdul Hamid Buang, 44, with a fractured left leg and ribs, a collapsed lung and bruises.

He was hospitalised for two months and given further medical leave until the end of November last year.

The other diver, Filippino Ryan Jay Carino Malubag, 22, suffered cuts and bruises. He received one week's medical leave.

The tanker's then-chief engineer Schzule Dietmar Fritz, 62, was fined $7,000 in a district court on Wednesday for hurting the two men through a negligent act.

According to court documents, the 243m-long Bahamas-registered tanker Shetland Spirit anchored off Singapore at the Eastern Petroleum Anchorage on Aug 18 last year.

It was to undergo refuelling and an inspection of its underwater hull before being transferred to a new owner.

The court heard that the ship has since been renamed.

Investigations revealed that at about noon on Aug 22, the captain ordered the engine generators and fuel pumps be started.

The court was told that a nearby ship was drifting and it appeared that there could be a collision if the Shetland Spirit was not moved.

Fritz, who assumed that the diving operation was over, also began 'blowing the engine' - without permission - to ensure that there were no leaks or debris in the engine cylinders. The process also caused the propeller to rotate.

Fritz would normally have been required to make a request to the bridge and receive orders from the captain before 'blowing the engine'.

'Blowing the engine', or turning the engine's drive shaft which is linked to the propeller, has to be done before the engine is actually started.

Pleading for leniency, Fritz' lawyer Mr Wee Pan Lee told the court that it was unusual for the captain to give the order to prepare the engine when the tanker was not scheduled to sail.

'It was reasonable for the accused to assume that there was an emergency,' he said.

The court heard that the two divers, who worked for DiveTech Marine Services, were taken to the Singapore General Hospital for treatment.

A DiveTech Marine spokesman told The Straits Times on Wednesday that the two divers have since fully recovered and returned to their jobs.

He said that the two men did not want to comment on the incident as they had 'been through enough'.

Fritz, who is a German national, has been seafaring since 1967.

He has been a chief engineer for more than 28 years on board 25 vessels and has an 'umblemished record' of service with his employers.

He could have been jailed for up to two years and fined.