The FBI says Robert McGill of Los Angeles is being held for the death of his wife Shirley aboard the Carnival Elation.
Carnival says the 55-year-old woman was killed during a domestic dispute on Tuesday evening as the ship was midway through a five-night trip to Cabo San Lucas. FBI and Carnival would not say how she was killed.
Crew members found the body and later detained McGill in the brig. The ship docked at its San Diego home port Thursday morning and the woman's body was removed.
Passengers say they never got official word but rumors flew after a security guard was posted outside the couple's cabin.