This is one of a few bags I had hoped to finish before our recent trip. The intent was for each kid to have a bag to carry their beach stuff in. Towels, goggles, toys, treasures. This one is made of canvas on the outside and a Michael Miller Robot fabric as it the lining.
I used the Everything Tote pattern from Heather Ross' Weekend Sewing book and downsized it to fit little bodies. I don't have any scientific method for doing this - it was pure winging it. I just pulled out the pattern, taped some 11x17 sheets of paper together and traced an intentical but smaller size for the bag shown below. I adjusted the handles and binding accordingly and it came out pretty well. The pocket is a little big but I'll adjust it on the next one.
As for the size, my downsize job is a little small for a towel, but it will fit everything else. In the meantime, it has been used for moving legos around.