[foobar1962]

Motor powered ships don't zig zag. Sail powered ships need to tack and gybe to go directly upwind and downwind, but TBH in busy harbours with navigation hazards and a lot of commercial traffic most would furl the sails and use the motor for safety.

You might be interested in "lead marks" which are two signs visible from a distance. They "lead" ships by providing a straight path through difficult passages when the two signs line up. Very simple and effective.

Note that modern lighthouse lights either rotate or blink, the flash frequency is unique and marked on charts to further help identify location at night.