I have my sight reduction tables somewhere, and in a small yacht with a fickle electrical system and no engineers/electricians, I'd also bring a sextant, if only to help pass the time, but if I was the skipper of a major navy ship, I'd expect reasonably good dead reckoning, inertial navigation, clues from sonar, maybe even water temperature, as well as radar pilotage in coastal areas, would be quite enough to find my way around...