With summer coming to an end, we decided to put our old tarp (that we used as a slip and slide) to good use. We have made this water blob before, a few years ago and it was lots of fun. We used an old painters tarp, that I folded three times over to make it extra leak proof.
Then, taking some parchment paper, I ironed all four sides of the tarp, sealing the edges. The parchment paper is really important, because just a little touch of the iron melts right through the tarp (I burned multiple holes by accident).
I did not get a picture of the next step, but you cut a small slit in a corner (making sure you get it to the middle of the layers). Then placing the cut side up, insert the hose and fill it. I filled mine a lot, because my children do belly flops and flips on it, I wanted it really soft! I used duct tape to seal the hole, and it worked surprisingly well. Try to get it as dry as possible before putting the duct tape over the hole. My blob did leak a little, but we still got about two hours of jumping out of it. It was sturdy enough for even me to jump on it. We had a lot of fun.