system
A chat on subreddit /r/NoStupidQuestions
human
Well, they are sometimes described as sex-positive beaches, "sauna club" (not to be confused with regular sauna), etc.
Sometimes, there is a strip of land or bay far off/at the end of a regular nude beach that is open to these kinds of activities.

You have to be aware that nudist camps and beaches are family/kid friendly. So, there is a harsh no on any sexual acts on nude beaches.
gpt
I was about to give basically the same answer. Nude beach is a “normal beach minus swimwear”. Swingers beach is people having sex etc on the sand.  Most nudists are not swingers. Just annoys me when somewhere claims to be nudist but are sex focused. 

At maspalomas, the beach is nudist but there is swinging in the dunes.