nearly three o’clock
Such thoughts had n't previously crossed my mind , and I was determined to keep on my guard . Meanwhile I had assumed this rest period would be the turning point in our stroll , but I was mistaken ; and instead of heading back to the Nautilus , Captain Nemo continued his daring excursion . The seafloor kept sinking , and its significantly steeper slope took us to greater depths . It must have been nearly three o'clock when we reached a narrow valley gouged between high , vertical walls and located 150 meters down . Thanks to the perfection of our equipment , we had thus gone ninety meters below the limit that nature had , until then , set on man 's underwater excursions . I say 150 meters , although I had no instruments for estimating this distance . But I knew that the sun 's rays , even in the clearest seas , could reach no deeper .