A strip of fabric and two minutes are all you need to make a lovely halter neck bikini top - at some point I'll make the bottoms to go with it! Credit to Larissa Art on Deviant Art for the woman body base I use in this how to http://larissa-art.deviantart.com/art/Doll-base-176036478
Take a strip of jersey or lycra (or other swimwear appropriate) fabric approx 1 meter long, and six inches wide (or however wide you need to cover all the important bits!). You can hem around it if you wish, but I didn't as my fabric isn't one which frays.
Slip your fabric under your arms and get it evenly spaced so the centre of the strip is in the centre of your back.
Tie the strip in a knot over your breast bone, then tie it behind your neck. You may be able to leave it as is if you've managed to get everything covered and secure - the more well endowed of us will probably need step four!
Pinch together the bottom sides of the strip under the knot until you feel less exposed (see the red line in the picture left). Pin together, slip your bikini top off and sew this seam on a sewing machine or by hand.