Tanya Streeter made a remarkable dive – on just one breath of air – to the unimaginable depth of 160 metres. This was a dive that nearly went very badly wrong. As Tanya tells Steve Backshall – himself a world-class adventurer – she blacked-out seconds before she began the dive; she developed nitrogen narcosis – almost like being drunk – and struggled to remember how to release the pin that would return her to the surface. On the way back up she thinks she blacked out for a second time.