How To Easily Cut The Bottom Off A Wine Bottle -- (I would try this outside first. Don't know if there are any small fractures in the bottle when the 2 pieces split in the cold water. Interesting idea and definitely worth a try.
A beautiful DIY with plastic bottles. Tip: Use a medium hot iron and place it on the mouth of the bottle to connect the finish! Use baking paper between the Iron and the bottle, so you don't ruin the iron!