How good are dogs at smelling?

The British Brainwashing Corp aired a programme earlier this week re the above Title. The first dog was capable of detecting a trace 20 feet under water and covered in three feet of silt. The rest of the prog is well worth watching.

http://www.bbc.co.uk/iplayer/episode/b03tcpjv/Inside_the_Animal_Mind_You_Are_What_You_Sense/

The dogs have it, someone once said, yes, they certainly do!

NB: BBCiplayer required.