Date: Around 2012.
Country of origin: Probably the U.S.
A single woman is traveling somewhere with her son (maybe 4-10 years old) on a boat or a ferry and the kid disappears.
Later she is asked to identify the dead body of a kid thought to be her's, but she says it's not her son.
Towards the end of the movie, she finds him alive on a beach, where some people are holding him captive.
It's not Kidnap (2017).