sail in uncharted waters

плавати в незнайомих водах (в прямому та переносному значенні) (Trade Minister Douglas Alexander told BBC ... that not only were the scenes in the Oval Office 'deeply troubling and sobering' but demonstrated 'in the starkest possible terms' the extent to which 'the world we've all experienced for the last 80 years' had changed, adding we that were in 'uncharted waters'. - https://www.bbc.com/news/live/cn5220x56pqt)