"Dark Waters" is the sixth episode of the sixth season of the American fantasy drama series Once Upon a Time, which aired on October 30, 2016.

The sixth season of the American ABC fantasy-drama series Once Upon a Time was ordered on March 3, 2016. It premiered on September 25, 2016, and concluded on May 14, 2017. The season is the last to feature the series' main storyline, with the seventh season seeing a soft reboot. Due to this, original cast members Ginnifer Goodwin, Jennifer Morrison, Josh Dallas and Jared S. Gilmore, as well as long-time cast members Emilie de Ravin and Rebecca Mader, all departed as series regulars after the season; all would make at least one appearance the following season.