Are we talking water that has been bottled and distributed or are we talking about you filling up a bottle yourself? Bottled waters are filled under sanitary conditions. They should be pretty much okay as long as they remain sealed. Water stored in plastic can acquire some plastic taste to them. If they weren't filled under sanitary conditions, bacteria can build up and cause severe health problems.
for drinking with a liquid thing like a water
All water sealed in plastic containers should be assumed to be potable (drinkable) except when the label expressly says otherwise. Typically, water sold in plastic bottles or multi-gallon jugs is marketed for taste and not for particular purity or cleanliness; but rest assured it is free of dangerous or particularly unhealthy substances, otherwise it would never make it to the shelves!
These plastic bottles are first shredded to produce plastic chips. Depending on what they will be recycled to make these plastic chips may or may not be melted.
Smell them - if they smell alright give them a good clean and they are safe to use. Pet bottles that have previously held stuff like oil however would be unsuitable as it is very hard to get rid of all the oil residue and minute amounts may remain and taint the water.
It's not the water that leaches, but the chemicals in the plastic leach into the water. It means that the plastic will break down a little and release some of its components into your drinking water, especially if you use it more than once.
It definitely decreases the amount of waste that comes from producing and disposing plastic water bottles.
plastic
plastic water bottle density
The answer is yes. You can definitely make a floating raft out of plastic water bottles. You would have to make sure that you had enough plastic bottles to complete the task. For step by step instructions visit http://www.wikihow.com/Make-a-Raft-out-of-Plastic-Bottles.
Potable water
yes
Plastic.