It’s the final challenge and perhaps the most dangerous yet. The scientists have to make a SCUBA device so that Kate can descend safely to the seabed some 5m down. It has to be sophisticated enough to supply her with breathable air at the right pressure, while giving her the freedom and time to explore beneath the waves. They only have access to the simplest tools and materials, however, and Kate has to put her trust in the team to get their Rough Science spot on this time. There can be no room for error.