"Nightswimming" is  interesting and quite unconventional! I'd say unconventional as a love triangle of sorts takes place in, of all places, a swimming facility, in the dead of the night.  The film gives viewers a peek of a young couple's  fickleness in terms of emotions and the uncertainty of their feelings for each one.  The watchman, the other person who becomes sort of the unwilling participant in this story of sorts,  seems to give  light in terms of the real essence of the relationship between the young couple.  Realizations were made and the last scene, that of the watchman skinny dippin' in the pool, seems like a fitting ending, as if  a sort of cleansing himself from last night's events.