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.