In the latest of the series that puts science to the test, the team takes on more fun experiments and challenges. Dallas Campbell traces the incredible global journey of 30,000 indestructible plastic ducks, while Liz Bonnin goes on manoeuvres at the bottom of the Baltic Sea in the Royal Navy's latest search and rescue sub. Dr Yan Wong challenges the people of Cardiff to take on the might of friction, and Jem Stansfield uses two domestic vacuum cleaners to climb up the side of a building. The programme is co-produced with The Open University. For more ways to put science to the test, go to the Hands-on Science area at www.bbc.co.uk/bang for details of our free roadshow touring the UK and activities that you can try at home.