In Sherlock series 1, the episode ending with Sherlock and Moriarty at a swimming pool is “The Great Game.”
“The Great Game” is the third and final episode of Sherlock’s first series, broadcast in 2010. Written by Mark Gatiss, it follows Sherlock as he investigates a sequence of apparently unrelated cases while an unseen criminal places timed challenges before him. The episode establishes Moriarty as the overarching opponent behind the games.
The closing scene takes place at a swimming pool and brings Sherlock, John, and Moriarty together in a tense confrontation. Andrew Scott plays Moriarty, while Benedict Cumberbatch and Martin Freeman play Sherlock Holmes and John Watson. The scene is sometimes confused with “The Reichenbach Fall,” which also centres on the rivalry but belongs to series 2 and ends at St Bartholomew’s Hospital.