I was able to get this sewn up for my massage therapist for her birthday that was this month.  It is a pattern that came with a kit I bought a few years ago.  I found out she loves flip flops (just like my oldest daughter) so I found this really cute fabric.  The screen material is a pliable fiber screen called “Pet Screen”.  You can purchase rolls of it at places like Home Depot, but they only have black or grey.  You can search and find it online in different colors.  We have a store out here called M& L Fabrics and they carry different colors.  I choose this tan for the sand color.  As I’ve made several bags before it was easy to do quickly.  But it has been a while since I made it so I did have to make some notes on the pattern for next time I make it.  I don’t think you can purchase this pattern anymore, but I will research and include a link if I find it.  She really loved it. Since there is no fabric at the bottom the sand will just fall out when she takes it to the beach.

Couldn’t find the this exact pattern (and it is copyrighted so I can’t just copy it here for you.)  But there are lots of other patterns out there that are similar (and some are even free).  Mine actually came as part of a kit for the bag.  I did make a few changes.  I used nylon webbing for the straps (easier than making my own straps out of fabric), and I added a loop with a clasp on it so she can attach her keys and they won’t end up in the bottom of the bag.