What do you call this device that floats in the water at ports?

I've seen lots of these, at ports, floating on the water:

I don't have a clue about what they are called.


light(ed) buoy

Images of lighted buoys

lighted buoy
Floating object used as beacon. Visual Dictionary illustration

light buoy

(Nautical) A buoy with a light on top which is lit at night to aid navigation. Wiki

buoy

A floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. Wiki