Glowing star things...

[Comfosa]

What are the glowing starry things that appear around the ocean and on the map? There are two just outside of London. Your ship will dead stop on them but they do no damage, and are also illuminated. A couple islands have a red star thing instead of the white one.

Are these relevant in some way? I can't seem to find any info on them, or I just missed it.

[ihfacny]

It is a buoy. See more on wikipedia.
It lights up a small area of the ocean = less terror build while you sail through the sphere of light

[Talon]

"Staying in the Shadows and avoiding the Light" (Thief:TDP) is a good way to go starkraving mad and die in this game.