I do have the large Kyss bag. It is a little heavy, but it holds all my junk I bring to the beach. I have my kindle, my husband's kindle and suntan lotion for the both of us. I can cram my towels inside too. it also has outside pockets for water bottles, etc. There is also an inside zip pocket that keeps the sand out of anything important. You can lock the outside zipper and wrap around your umbrella or chair and it's pretty safe.
I use it as a carry-on on the plane also. Hope this info helps.