Melissa Benoist in the hot tub from an upcoming Season 3 episode.
Behind the scenes footage shot by spectators while filming the Season 2x22 wetlook catfight in a Vancouver fountain.
In the Vancouver footage you can clearly see Melissa's body double, actress Lindsay Sporrer, in some scenes. One presumes that Lindsay also does the pool stunt scene in Season 3, so she should have been in the hot tub with Melissa.
Upgrade to Wamflix-Plus to view the full videos.