Castaway on the Moon (2009)

Mr. Kim is jobless, lost in debt and has been dumped by his girlfriend. He decides to end it all by jumping into the Han River - only to find himself washed up on a small, mid-river island. He soon abandons thoughts of suicide or rescue and begins a new life as a castaway. His antics catch the attention of a young woman whose apartment overlooks the river. Her discovery changes both their lives.

Source: TMDb