This woman seemed to have gotten away with the crime until someone dropped a tip to police about her:

A woman who allegedly killed her husband for insurance compensation in 2019 was arrested in the north of Seoul with her accomplice, the police said Saturday.
The police arrested the 31-year-old murder suspect, Lee Eun-hae, and the 30-year-old accomplice, Cho Hyun-soo, at a residential building in Goyang, just northwest of Seoul, at around noon, according to the Incheon Metropolitan Police.
As they arrived at a police station in Goyang, Lee and Cho declined to comment to reporters.
Investigators were able to locate the two as Lee’s father told police their address, saying his daughter is willing to turn herself in. The two did not resist during the process, the police added.
Yonhap
You can read more at the link, but she is alleged to have tried to poison her husband earlier in 2019 as well before successfully drowning him.