I bought this dry bag for an upcoming backpacking/camping trip. I was planning on using it for phones, passports, tickets, chargers etc - things that don't mix very well with water.
I thought a 5L capacity would be just about able to accomodate these items, but I was pleasantly surprised when the bag arrived. It's actually very spacious and versatile.
Its foremost function is obviously use as a waterproof bag, rolled up and sealed (which does decrease its size quite a bit), but with a convenient shoulder strap it also doubles up into a rather useful beach bag. You can fit trunks, travel towel, water, wallet, teeshirt and sun cream into it without sealing the hem - not bad for a 5L bag.
Some might say that not sealing it defeats the object, but unless you're planning on actually lobbing this item into the sea, it can be easily doubled up as a handy beach bag.
And, hell, if you do fancy lobbing it into the sea, all you have to do is fold it up and seal it and fire away; your stuff will stay as dry as a bone. Excellent value for money - this bag offers 100% protection from water whilst doubling up as a beach bag or even a daysack liner.