From The Daily Telegraph:
The gravity-defying garment, which has been christened the Demikini, allows women to develop a tan free from strap marks.
Wearers apply a gel solution under the arm which fixes the fabric to their skin.
"The gel is most commonly used in operations, but feels very comfortable and lets the wearer jump and bounce around as much as they want," said a spokesman for manufacturer the Stirling Group.
Here's another photo. In the, ahem, interest of science.
Seems like a keeping a supply of the gel on hand is a lot of trouble just to get a tan without strap marks, but what do I know. I'm from North Dakota where its apparently going to snow year-round from now on.