try the Totally Versatile Super-Sized Tote. I got the pattern on Craftsy, but the designer has it on Etsy, too.
This pattern seems too easy to have gotten such an nice bag! This is a BIG bag at 22" wide, 14" high, and 8" deep. It will make a great beach bag. There are two huge beach towels in there with lots more room for other beachy essentials.
Both sides of the lining have pockets as well. You, of course, get to decide the size of the inside pockets. I tested to make sure my Kindle in its case would fit in one. Gotta have my Kindle with me.
I only made one change--so unlike me. I added that flap with a snap thinking it would hold things in if it tipped, but I'm not really happy with how it pulls on the fabric when in use.
It does look nice when it's not too full, though.
Last, it folds up nicely if your packing for a vacation.
Definitely want to make a few more of these.