(Amphitrite was the wife of the sea-god Poseidon, and is the female personification of the sounds of the sea).
The curtain rises to reveal a large circular cutout in a screen, covered with a transparent fabric. The background is a scene of clouds and sky; at the front and bottom of the stage is a screen showing the sea.
On command, the performer — a lady it must be because of the name of the illusion! — appears in the sky and swims and does aqua-gymnastics, turning around and around in either direction. At the end of the performance, she takes up a dive position and plunges behind the sea.
The back of the stage is composed of the sky and clouds scene. The sea can be a picture or could be a projected movie — no mystery there. The key to the illusion is a pane of glass fixed to the front and top of the scene, extending at an angle of 45 degrees backwards. The lady is dressed in a bright, spangly costume and her skin is enhanced with white powder. She lies on a circular table at the bottom of the set, which is covered with dead-black material. The table can be rotated in either direction and moved backwards and forward. She is illuminated with a very bright light: this can be turned on gradually at the beginning of the performance, so as to create the illusion of a gradual manifestation: the table must be in position at the start of the performance. At the end, once she takes the dive position, the table is pulled away and she disappears.
This is an illusion best performed in a reasonably small space. It could be done upon a regular stage but loses its effectiveness if seen from too far away. If it is presented in the same show with the Three-headed Lady, it should be performed before the latter: as the principle is the same in both cases showing the Lady first would give the trick away. It may be tempting to dress the lady in something skimpy but the real point is her apparent materialization and disappearance, so don't over-undress her!
The glass must be absolutely clean.