So, these shorts keep popping up on pinterest. Aren't they pretty? They're also about $150 from letarte swimwear. Madness!

I'm also going to give you a written step by step of the bottom bit, which is just a pineapple motif, you may need to adjust the number of stitches involved to match the motif in the shorts (I counted 7 TR in the first round)
The first bit, the waist band is super easy, Just single crochet until the chain is as long as your waist (or hips-wherever you want them to sit) is wide. Then continue on back and forth until your piece is as wide as you like it. Remember you're going to fold it over and sew it into a tube for the ribbon to tie your finished shorts. It looks like they do a round of shell stitches along one edge of the waistband as well.
The next bit is just a bunch of these pretty circles:
Notes. join each round,
R1: 12 DC in magic ring. join.
R2: Ch 3 dc in same (counts as 2). 2 in each around (24).
R3: ch 3, 2 dc in same stitch (cluster) **Ch 2, 3DC in next stitch** (Repeat around)
Join last cluster to ch3 (don't chain 2 after)
R4:Ch 6, slst to ch2 space, **Ch 5 slst to space** last stitch is Ch2 & join to ch6.
R5: Ch 6, 5 DC in Chain space, ch 5, 5 dc in same ch Space,
**Ch 5 slst next sp 3 times, ch 5, 5 dc in next ch space, ch 5 sc in same ch space** repeat 5 times,
last stitch is Ch 5 slst next sp 3 times. join.
fasten off.

I counted 7 Trebles in the shorts but the closest chart I could find has 9, So it'll do.
Written instructions are as follows:
R1:Chain 4 (counts as first double crochet).
R2:Work (1 double crochet, chain 2, 2 double crochet) all in the 4th chain from the hook.
R3:Chain 4 to turn (counts as first treble), work 6 trebles in the chain-2 space.
R4:Chain 4 to turn (counts as first treble), skip first treble, work (chain 1, treble) in each treble across, ending with the last treble worked in the top of the chain-4.Turn.
R5: Work (chain 3, single crochet) in the first chain-1 space, (chain 3, single crochet) in each chain-1 space across. Turn.
R6: Skip the first chain-3 space, work (chain 3, single crochet) in each chain-3 space across.Turn.
R7:Skip the first chain-3 space, work (chain 3, single crochet) in each chain-3 space across (you will have one less chain-3 space at the end of each row).
On following rows, continue to repeat step 7; eventually you will have a row with only one chain-3 in that row. Fasten off.
Well, there it is, folks. Good luck!
EDIT: I recently saw a link to this page which shows the construction of these shorts using circle motifs. I would imagine you might find it helpful.
Also I finally found the post I saved the chart for the circle motif from right here