Tonga's solicitor general, Aminiasi Kefu, says the Crown is appealing what it considers the light sentences given to the skipper and first mate of the Princess Ashika, which sank two years ago with a loss of 74 lives.
In a trial earlier this year, the skipper Viliami Tu'ipulotu was jailed for four years but the sentence was suspended for three and a half years.
The first mate, Semisi Pomale, was jailed for five years and this was also suspended for three and a half.
Both had been convicted of a number of charges included manslaughter by negligence.
Aminiasi Kefu says they contend the judge erred in granting such lengthy suspensions.
"Under the statute you can only suspend a sentence for a three year period but he'd imposed a suspended sentence of three and a half years. So we are just fixing that up as a matter of technicality. At the end of the day the accused will have a lighter sentence."
Aminiasi Kefu says the former chief executive of the Shipping Corporation of Polynesia, John Jonesse, who was jailed for five years, is appealing both his conviction and sentence.
He says it's possible he could get a similar partially suspended sentence.