This video details what Thoroseal mixed with Acryl-60 looks like. I resealed my lower and middle ponds on 14 Sep 2013. I had originally built the shelves in the waterfall area with Mortar which was a bad idea. Always try use concrete for everything and leave mortar to what it is meant to be used for and that is for beneath concrete blocks. I also used mortar for the sides which gives it the smooth look, but just be warned it may deteriorate over time.
I used one bag of Thoroseal in this video and about 1/4 mix of Acryl-60 from a 1 Gallon Bottle.
You should be able to buy Thoroseal at any hardware distributor, but I get mine from Ace Hardware, you can also order off Amazon.com