I hesitated to make this post because it's not super impressive. But, hey, it fills a need, is really cheap, and the pool float can be repurposed to become a backpacking sleeping pad again, so here you go.
Basically, you can use a standard cheapo backpacking pad as a great pool float. I used it just as it was, and it was okay, except for one thing. And that was that my ears were right in the water, which is annoying.
So, I added some floatation to the head end. I rolled the short side over, and poked a string through to keep it rolled up. See the picture for details. Then I added a piece of a pool float to the inside, to give it more floatation.
And voila - a super comfortable pool float, great for sunning yourself in a lake or pool. And if you need it as a sleeping pad, just untie the string.
Also, that cord with a toggle that you see in the very first picture, tying it up - that's a DIY device as well. I got the idea from this felix immler video - . It's a very useful little trick, you can make it for free (assuming you have the cord) and I use it for tying up all kinds of things.