It happened just 11 days after a wedding in Birmingham, Alabama, in 2003.
The couple spent their honeymoon at the Great Barrier Reef. Prosecutors say 26-year-old Tina Watson drowned when her husband turned off her oxygen tank while diving.
Charges against 31-year-old Gabe Watson were filed five years after her death because prosecutors say the case is so complex
"You never think your daughter will leave for her honeymoon and her husband will kill her," said Cindy Thomas, mother of the victim.
Watson says he's innocent. Prosecutors say the motive was money because just before the wedding Watson asked his then fiance to increase her life insurance policy to the maximum while making him the beneficiary.