A reference to slingshots in a story, although its referred to as sideless g-string. The second bikini describes sounds similar to a purple bikini Marina Kali wears on the CoverModels website. I'll post a link in a minute.
"This was the longest we spent in any one store all day, but Kelly finally picked out two swimsuits she really liked for me. The first was a lycra sideless g-string, it was basically a V of fabric that started at my crotch, went over my shoulders and was connected to a Y shaped string back that ran up between my ass cheeks and attached to the front at my shoulders. The other suit she bought me was a bright red one-piece suit with a front that plunged almost indecently low and was connected by thin clear strapping and a thong back that was attached the front by a string at the waist. The top also tied behind my neck. This suit was basically a thicker version of the other one. When I mentioned this to Kelly he response was, 'Well you have to have something to wear in the pool when Jen's around, but I still want you to look sexy too.' It made sense to me so we bought the swimsuits"
Here the link to the full story.
Literotica.com - Lesbian Sex - My Best Friend's Mom