So this has not a thing to do with the beach, but it was my idea after much searching the Internet and stressing over cutting into a formal dress. It came down to the day of the dance, and I had to put scissors to the dress. Maybe this can help another mom who thinks this project should be grounds for Valium or Xanax - not a whole bottle but 1 pill. But since that idea isn't likely to be very popular with your doctor, let me prescribe what I took to enable me to cope: Dr Pepper and chocolate. True Story. And what's more - it worked. I got in the groove and got it done without mishap.
My daughter had 2 formal dresses. One was purchased by her grandparents at the Mall of America, and they graciously paid for professional alterations. The length that was cut off was given to us, and I used it as a guide. A skirt or maybe even a round tablecloth could have sufficed. Having a rounded edge really helped.
I had her put on the dress with her shoes and measured how much it needed shortened then went just a bit longer, I believe it was 1/2". I cans lined up the hem and pinned the front layer to the back along the edge so it wouldn't slip during cutting. I measured along the hem, but I honestly mainly eyed it as I laid the fabric scrap down as a cutting guide and weighted it with cans.
I used lots of cans to keep the slick fabric from sliding out of place.
I lined it up until the curve was off or I was running out of cutting mat, whichever came first.
I was able to do a large section, but as I got one shot at it, I did all of this slowly and carefully.
I used a rotary cutter and went slowly, smoothly, and pressed hard. There were places it didn't cut all the way through, so I'd suggest a brand new blade or just being prepared to do a little cutting here or there. Carefully pull the extra away slightly, so if you need to cut it will be smooth and blend right in.
Even though I was slow, careful, even methodical, this went quickly. It was a fabric that didn't require a finished hem, so cutting was all I had to do. In fact, had I tried to finish the edge, I would have had a fight not to have a mess. I experimented on the scrap and was very glad to leave the edge raw.
And here's the finished dress after my masterful cutting of the hem! Looks like we needed some masterful cutting of grass judging by the dandelions at her feet.