as a young man he 'd never considered time as anything other than a current to bear him aloft , propel him into his future , now he understood that time is a rising tide , implacable inexorable unstoppable rising tide , now at the ankles , now the knees , rising to the thighs , to the groin and the torso and to the chin , ever rising , a dark water of utter mystery propelling us forward not into the future but into infinity , which is oblivion .