Some time in the summer of 1985, Billy had Heather got jobs at the community pool as lifeguards.
The pool is first shown in the season on June 30th, 1985, when its Billy's turn to lifeguard. He walks down the pool, passing Heather and some of the Hawkins moms, who had come down to the pool to flirt with him. Later that day, Billy goes up to Ms. Wheeler after watching her swim, and asks her on a date.
After getting Flayed the night before, a dazed Billy returns to the pool to do his job. The Mind Flayer urges him to kidnap someone at the pool to bring to the Brimborn Steel Works, and he nearly takes Ms. Wheeler when she tries to talk to him in the storage room minutes before his job. Billy resists the urge, but it eventually becomes to much for him and, when he gets the chance, knocks out and kidnaps his co-worker Heather.
Later, when the Party (minus Dustin) figures out that Billy is Flayed, they devise a plan to lure Billy into the pool's sauna after hours and burn the Mind Flayer out of him, similar to what they did with Will the previous year. The plan is going well until they realize that they underestimated Flayed Billy's strength: He breaks out of the sauna and nearly chokes El to death before she is saved by Mike. Before a Flayed Billy could hurt Mike, El uses her powers to save him and to fling Billy through a wall and he escapes.
Behind the Scenes
The filming location of the pool was South Bend Pool, 2000 Lakewood Avenue SE, Atlanta Ga. The location is only about 1/2 mile from Screen Gems Studios, where most of the interior scenes of Stranger Things are filmed.