An orgy is a gathering where guests freely engage in open and unrestrained sexual activity or group sex; and a bunga bunga orgy is an orgy in which participants have sex underwater, such as in a swimming pool or a hot tub.
Partners can engage in penetrative sex, known as "full swap", or choose to "soft swap" in which they engage only in non-penetrative sex.
New swinging couples often choose a soft swap before they are comfortable with a full swap, although many couples stay soft swap for personal reasons.
A sex party is a gathering at which sexual activity takes place.
Sex parties may be organized to enable people to engage in casual sexual activity or for swinging couples or people interested in group sex to meet, but any gathering where sexual activity is anticipated can be called a sex party.
Group sex also occurs in populations of non-human animals such as bonobo apes and chimpanzees.
Group sex most commonly takes place in a private sex party or semi-public swinger gathering, but may also take place at massage parlors or brothels or, in some jurisdictions, at purpose-built locations such as sex clubs.
In places where non-monogamous sex is taboo or illegal, group sex may take place in private or clandestine locations including homes, hotel rooms, or private clubs.
Fantasies of group sex are extremely common among both men and women, and group sex is a subgenre in pornographic films.
Group sex is sexual behavior involving more than two participants.