A sex act in which a woman (or man), in a crouching position, places their eye upon the anus of a standing male partner. They then proceed to grasp the shaft of the "periscope". Advanced users can then proceed to adjust the knobs of the periscope. The move is finished with a successful load blown, and a cry from the gazer of "fire the torpedos" as the recipient lets loose a fart. The fart should be moist so the gazer receives a maritime spraying of ocean wind.
Jim: Hey, uh betty. Ever looked through a swedish periscope?
Betty: Nope whats that?
Jim: come back home with me and ill show ya