Over  the past few years, when I've purchased swimwear, I've focused almost  exclusively on bikinis. I have one distinctly athletic tank suit that I  wear when I want to be, well, athletic, and not worry about my suit  falling off. But for your average day spent poolside or a casual dip in  the ocean, I almost always gravitate to a two-piece.
This  year, though, growing bored with my selection of bikinis (I have a  substantial amount of swimwear for someone who maybe goes swimming twice  a year), I was delighted to read that one-piece swimsuits are becoming  increasingly common. I decided to take advantage of their new popularity  by finding one of my own. My only requirement was that it not be  boring.
 
Eventually  I found what I was looking for in a green-and-black striped suit with  some flattering princess seams I couldn't pass up. There were several of  the same suit available secondhand on eBay, so I waited until I found  one under ten dollars, and then made my move. It was perfect. But only  when I tried it on a second time, long after I could have conceivably  returned it, I was disappointed to notice that it was too short for my  torso (now I see why there were so many of them for sale)!  
No  matter how I tugged it, either the bust would slide down to an unseemly  level, or the leg openings would ride up to a height last seen on Baywatch.  I've observed that high-cut swimsuit legs are currently coming back  into fashion, but I've never found the style flattering, and I certainly  didn't want to rock it myself!
However,  the overall styling of the swimsuit was very similar to the  retro/pinup/50's styles that continue to be a fringe fashion staple  today. I decided I'd cut up my swimsuit and turn it from a one-piece to a  high-waisted two-piece.
I have to  say in advance that I did it wrong—so very wrong. I had no idea working  with elastic fabric would be such a tribulation! While the finished  product looks passable from a distance, I'm absolutely flustered by the  disastrous nature of the work that got it there. But here, I'll let you  judge for yourself!
I measured the spot where I ultimately wanted the waistband of the bottoms to lie, added an inch, and cut it.
 
I  thought I was being smart by following the horizontal stripes, but as I  finally got around to the other side, I learned that they hadn't been  sewn perfectly straight—I'd lost almost an inch in height from one side  of the front to the other. Mistake #1! 
Also,  since the suit was made of two layers with a lot of gathers, I had cut  the inside a lot lower than the outside, thus losing even more effective  height. Mistake #2!
With  nowhere to go but forward, I hemmed the waistband of the bottoms. I  kind of wanted to put some sort of elastic band there, but in examining  most of my other swimsuits, they didn't actually seem to have one, so I  decided to do without it. Instead, I simply rolled the material under  twice, then topstitched. Sadly, this was Mistake #3, as  some parts of  the inner layer were too short to actually make it into the hem.  Fortunately swimsuit knits don't unravel easily, so I haven't bothered  to fix this mistake yet. 
I started out with a stretch straight stitch on my machine, but that was taking forever,  and seemed to be causing the material to pucker, so midway through, I  switched to a three-step zigzag. As you can see, even in the few places  where the zigzag itself turned out decent, it still made my suit  waistband "do the wave."
When  I tried the suit on after finishing the waist, I found that it had  stretched quite a bit and now didn't hug my body. My solution was to  open up about an inch of each of the seams in the front and then re-sew  them a little tighter. The picture at left shows an inside view of this  correction.
With the bottoms done (at least as  done as I could stand to make them without crying!), I started on the  top. By "started," I mean I stuffed it into the bottom of my Projects  Box so I could "think" about the best way to finish it. Three months  later, I could not procrastinate any more. I consulted the internet  about ways to sew elastic material.
While  some tips were totally useless to me (buy a walking foot? Sounds nifty!  Costs almost as much as my entire sewing machine? Next!), one, which  advised sewing over a piece of paper, sounded like it might actually  work. Since I'd had trouble keeping all the material together when I  sewed the bottoms, I also decided to glue the hems down prior to sewing  (usually I just use pins). I was proud of myself for taking this extra  step in the name of quality, but alas! It was Mistake #4—the glue  (Aleene's No-Sew temporary fabric glue) wouldn't hold the material, so  all I did was make it goopy and unworkable until it dried.

As  you can see from the picture, I also glued a narrow strip of paper to  the top of the piece. The paper may or may not have been Mistake #5. It  certainly didn't 
seem to stop the fabric from puckering, but it  did make quite a mess in terms of removal. I had to soak it in water  until it dissolved in order to get all of it off, and I can still see  bits of it stuck to the seam—even after a soak, a wash, and a swim in  the Chesapeake Bay!
 
I  can no longer remember if I had the bright idea to reduce my thread  tension while sewing the top, but if that's what I did, it was certainly  Mistake #6! For whatever reason, the topstitching on my bikini top is  loose, erratic, and unraveling. It looks less like a triple-step zigzag  and more like a seismograph during an earthquake!
Even  after all these mistakes, I nonetheless thought I had a Minimum Viable  Product that I could at least wear once to the beach before throwing it  away in despair (or before all the seams come out and I'm left  accidentally skinny-dipping!).
So I wore it to go stand-up paddleboarding on Sunday evening!
I  am proud to say that at no point did I end up accidentally skinny  dipping, and the suit looks much the same now as it did before I  started. However, I think after I get it out of the laundry, I might  undo all my work and have another go at making seams that don't look  like I sewed them while riding a roller coaster!