The Breath (1995)

Haida, once a famous private detective, is now down and out and running out of reasons to live. One day, while engaging in a group volunteer project to clean up a river, he loses what's left of his will to live and lets the water carry him away. He ends up rescuing a drowning man who alters his view of life totally. Soon he gets a job investigating the mysterious disappearance of a student who sent her mother a cryptic letter, "Wait a bit, Mother. I'm sending my breath. It will arrive soon."