Of course, I found it on Pinterest

And it was a hit. Yes, big daddy man and little man spent HOURS slipping playing around on the slowly leaking water bed.

http://www.gokidyourself.com/2012/03/giant-squishy-sensory-bag.html
The link (copy and paste it, blogger is having linking issues) I used and the original source here:

http://playathomemom3.blogspot.com/2012/02/redneck-waterbed.html

They must have used a gallon of food coloring; we didn't get a that lovely shade of blue in their pictures, I even wasted used the whole tube. I digress, it was still a load of afternoon fun! You should try it and tell me about it. Off to rescue baby girl she is stuck under the end table...again.