Shiomi High School, like any other high school in anime and manga, has its own swimming pool for physical education classes in summer. This place is where the Shiomi swim club holds its club activates and where Souya Minamino practices swimming. It is also the place that Mitsumi Seto talked about her future of wanting to become a lifeguard.
This place makes an appearance in Season 1Episode 46 and Chapter 516. In the anime, the ghost of a baseball club manager haunted the area. Isumi Saginomiya came here to send this spirit to heaven. This caused Wataru Tachibana to misunderstand the situation and challenge the baseball team ace to a one-pitch match for Isumi's heart.