The captain and navigation officer of the cargo ship Rena that grounded on Astrolabe Reef have been sentenced to seven months jail.

The ship's captain Mauro Balomaga, 44, and navigation officer Leonil Relon, 37, both received seven months jail when the appeared for sentencing in Tauranga District Court today.

The navigation officer and captain in Tauranga District Court today.

On February 29 this year Balomaga pleaded guilty to all charges, while Relon pleaded guilty to all but one charge under the Resource Management Act.

Both men faced the same charges under the Maritime Transport Act 1994 for operating a vessel in a manner likely to cause danger, under the Resource Management Act 1991 for discharging a contaminant and on three charges under the Crimes Act for altering ship documents.

The captain also pleaded guilty to one additional charge under the Crimes Act for altering ship documents.

The cargo ship Rena ran aground on Astrolabe Reef about 25km off the coast of Tauranga on October 5, 2011 subsequently spilling hundreds of tonnes of oil into the sea.

In sentencing today Judge Robert Wolff a clear message needs to be sent that where there's a disaster those involved need to be truthful so solutions can be found as soon as possible.

He said reports the immigration department would immediately deport the men if they received anything less than a jail sentence had no bearing on his sentencing decision.

He earlier remarked that the Immigration Department's decision to deny visas to the men's wives at Christmas could also have a bearing on sentence.

He started the sentencing at two years based on the men falsifying the navigation records to cover up the poor navigation and bridge communication practices that ended with the ship striking the reef.

The offence under the Crimes Act carries a maximum penalty of seven years jail.

The sentenced was reduced by a year due to the length of time the men have been on bail, the second officer in a hotel in Te Puke, the captain in Rotorua.

The judge also gave credit for the men's decision to take part in two Marae meetings and make their personal apologies to the coastal iwi for the damage they were responsible for.

A further three months was reduced for entering guilty pleas.

On the Maritime Transport Act charges of operating a ship in a manner which caused unnecessary danger or risk, he also sentenced the men to seven months, concurrent with the Crimes Act sentence.

No sentence was given on the Resource Management Act charge on the offence of discharging contaminants into the coastal marine environment.

The charge carries maximum penalty of two years jail and fines of $300,000 or $10,000 each day the offence continues.

It was ruled the actions of the men although argued by the Prosecutor for the Crown Rob Ronayne as 'incompetence verging on recklessness” did not satisfy the definition of recklessness itself and the two did not receive a fine.

It was an argument raised earlier by the master's counsel Paul Mabey QC is his plea for a home detention sentence.

As they are both foreign seamen they cannot be jailed on the RMA charge.

Judge Wolff said on the RMA charge he would have given them longer than seven months because of the level and scale of the disaster.

'But I am required to follow the letter of the law, and I can impose no sentence on that charge.”

The court heard today how in the hours leading up to the grounding of the Rena on Astrolabe Reef the ship's crew failed to comply with ‘basic principles of navigation'.

The summary reveals the Rena deviated from the passage plan after leaving its previous port of Napier on October 4 travelling close to the submerged reef Bull Rocks, Arial Bank and the shallows of Arial Rock.

At one point the ship was 5.8 nautical miles off the approved passage plan.

At about 1.35am on October 5 the navigation officer altered the course of the Rena to 252° substantially deviating from the approved passage and putting Rena on track to hit the reef.

He then called the captain to the bridge and informed him of the change.

Prosecutor for the Crown, Rob Ronayne, says the Rena struck the reef because the officers on watch cut corners and navigated the ship incompetently in breach of ship regulations and the captain's own standing orders.

The summary states when the captain came onto the bridge he did not check the alteration of the course or the ship's position in relation to the passage plan. He also failed to transfer the ship's position to a larger and more appropriately scaled map showing navigational hazards including the Astrolabe Reef in more detail.

Approximately 10 minutes and 15 seconds before the ship grounded, the Astrolabe Reef appeared on the ship's radar.

At this time the ship was three nautical miles from the reef and on direct course to hit it.

The summary of facts reveals the Rena was 2.6 nautical miles from the reef when the captain noticed it on the radar and believed it was a small vessel or false echo.

The court heard that at no stage did the captain instruct any action to be taken to avoid colliding with the object on the radar.

The ship struck the reef at 2.14am.

The court was told that after the grounding the captain instructed the navigational officer to alter the chart and the passage plan.

The captain also made a further addition to the chart to appear as though Rena was planning to pass clear of the reef.

The captain's lawyer Paul Mabey QC argued for home detention for his client.

'It was a hopeless case of a coverup.

'There is no evidence of recklessness.”

He also said the captain and crew of the Rena had identified the oil leak and were taking steps to stop it when the control of the ship was taken out of their hands.

Both men later admitted making changes to the ship's GPS log and passage plan and misleading authorities when earlier interviewed by authories.

The owners of the Rena cargo ship Costamare's subsidiary Daina Shipping has also been charged by Maritime New Zealand under the Resource Management Act.

That case has been adjourned until July 18.

The grounding of the ship is so far estimated to have cost more than $130million.