where is the clearest water in the world located?

Hello Birkett7

What an interesting question!  There are many places that claim to
have the "clearest water in the world" but not many back it up with
any facts or figures so I have discounted these.  The results I was
able to obtain appear to show a visibility around 60m to be the
winner.  Several locations claimed visibilities of 40-50m and claimed
to be the "clearest water" but only a handful reached 60m.

According to the Virtual New Zealand website Te Waikoropupu Springs
near Takaka, New Zealand has the clearest fresh water in the world. 
The clearest water in the world being the sea-water under the
Antartica ice shelf as it is unblemished by humans.

The horizontal visibility at Te Waikoropupu Springs is 62m. 

Nearby there is also the Pupu Springs (also fed by the Takaka river)
which has visibility rated at 60m.

These are both world-famous locations for water sports and diving.

http://www.vnz.co.nz/photos/rivers/index.shtml
http://www.marrserv.com/dinza007.htm
http://www.newzealandoutdoors.co.nz/rafting-kayaking/nelson.html

I hope this answer satisfies your curiosity but if it does not please
ask for clarification and I will do all I can to help you out.

superb, thank you!