Especially when flying, a travel blanket is a great thing to bring along. The ones they give you on the plane are never seem to be quite big enough and may not even be washed. Besides, once you land, what help is that little plastic wrapped guy going to be on a beach? A Deck Towel offers a light, portable, and good looking way to block out chatty neighbors, and it might even come in handy when you land.
And regarding dckaapys just take a small bag you’d use at home to go into town (something that fits your purse/camera/small guidebook in). You can put things in it when it’s being stored in your rucksack (ie. when you’re schlepping that around!) and it saves you buying something new. Otherwise, remember you can always buy cheap, small bags at markets, so don’t worry too much!
I LOVE Deck towels. I have one I use as a table cloth for a small table.