An Alabama man convicted in his wife's honeymoon scuba diving death is facing a harsher punishment after being sent to jail for a year.

David Gabriel Watson, 32, of Birmingham, was sentenced earlier this month to serve one year of a four-and-a-half year sentence for manslaughter.

His wife, Christina Watson, drowned on the Great Barrier Reef in 2003 on a scuba diving trip with her husband after being married for just 11 days. The 26-year-old's body was found on the ocean floor.

David Watson was to stand trial for murder, which carried a potential life sentence, until a guilty plea to the lesser charge was accepted.

"I have formed the view that this sentence is manifestly inadequate," Queensland Attorney General Cameron Dick said, while announcing an appeal for a longer jail term.

Coroner David Glasgow formally charged Watson with murder last June, saying it was likely that Watson killed his wife by holding her underwater and turning off her air supply.

The coroner said a possible motive was Christina Watson's modest life insurance policy.

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