Satellite image obtained courtesy of Maxar Technologies shows a close-up view of the forward section of the MV Wahashio shipwreck off the coast of Mauritius on August 19. Photo: VCG

The captain and first mate of an oil freighter that crashed into a coral reef off Mauritius, unleashing the Indian Ocean archipelago's worst environmental disaster, will be released "imminently" after their 20-month sentence was commuted Monday, a lawyer said.

The MV Wakashio, a Japanese-owned but Panamanian-flagged vessel, ran aground in July 2020, spilling more than 1,000 tons of toxic fuel into pristine waters, coating mangroves, corals and other fragile ecosystems.

The two men, who have been in police custody since August 2020, were convicted last week and sentenced on Monday, with magistrate Ida Dookhy Rambarrun noting that the court had taken "into consideration the fact that both defendants pleaded guilty and apologized."

Kushal Lobine, who represents the ship's insurers Japan P&I, said the sentences had been commuted on the grounds of good behavior and 16 months of time served, allowing the pair to return home.

"Their departure is imminent. The captain will return to India and the other to Sri Lanka, their respective countries," Lobine said.

The vessel's captain, Sunil Kumar Nandeshwar, and first officer, Hitihanillage Subhoda Janendra Tilakaratna, were found guilty of "endangering safe navigation."

"The captain and his second in command were irresponsible and did not deliver as they should on their 'navigational duties,'" the magistrate said on Monday.

The MV Wakashio was sailing from Singapore to Brazil with 3,800 tons of fuel oil and 200 tons of diesel aboard when it ran into the reef off the southeast coast of Mauritius.

During the trial, the captain admitted drinking during an onboard birthday party and said he had given instructions to approach Mauritian waters in order to gain access to a phone network so that crew members could contact their families.

"The sea was bad, but the visibility was clear and it was safe to navigate... At one point, the ship could not move and had touched the sea floor," Nandeshwar said.

"Since I had had a few drinks, it did not seem worthwhile to intervene and it did not occur to me that we were sailing that close."

More than 1,000 tons of oil seeped into waters full of marine life from a gash in the vessel's hull before salvage crews were able to remove all the remaining fuel.

AFP