It is mutual consent that makes a clear legal and ethical distinction between BDSM and such crimes as sexual assault or domestic violence. Depictions of male and female masturbation are common in pornography, including gay pornography. Masturbation has been depicted in art since prehistoric times and is mentioned and discussed in very early writings. Real enema shots or videos of true medical situations may violate privacy laws in some countries. It is commonly depicted in pornography, but very rarely in mainstream cinema. The person receiving anilingus is regarded as the passive partner in the act, and the person performing anilingus is the active partner. When he is in position the cover is closed. Clothed female, naked male is a genre of erotica featuring one or more nude men and one or more clothed women. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the nine substitute exercises for penetrative lesbian hentai sexual activities, as detailed in the Paradis Charnels of 1903. Pornographic films present sexual fantasies and usually include erotically stimulating material such as nudity. 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. After the prerequisite level of sexual stimulation has been achieved, and ejaculation becomes imminent, the male will position his penis so that the semen discharged will be deposited onto his partner face. In milf xxx September 2003 the BBC reported on the new dogging craze. Pornographic films are generally classified into sub-genres which describe the sexual fantasy which the film and actors attempt to create. Participants usually derive pleasure from this, even though many of the practices—such as inflicting pain or humiliation or being restrained—would be unpleasant under other circumstances. Individuals who can change between top/dominant and bottom/submissive videos porno gay roles—whether from relationship to relationship or within a given relationship—are known as switches, though the term switch in this context is occasionally seen as derogatory and is rejected by many who might simplistically fit the definition.