Crowded waters, traffic moving at 15+ kts, in both directions, limited room to manuever leaves little or no time to employ traditional navigation tools.
Based on the measurement of the height of a star, the use of the traditional sextant requires a good mastery of the instrument, a stability of the user, a visibility of the horizon, a hypothesis on its position and the capacity to use astronomical tables.
(HAND HELD) STARNAV used the skills acquired in astral navigation to develop an autonomous system able to determine the position of the user by observing the astres.
The system is composed of a camera and an inertial platform. By aiming at an astre (Sun, Moon, Planet, star), without knowledge of the target (recognition algorithm), without visibility on the horizon, without astronomical knowledge, the system determines the position on Earth.
https://www.starnav.fr/site/en/electronic-sextant-g-stell/
IIRC Uncle Sam has the patents on similar devices, there several of them out there.