I speak out over ocean waves,
Flag on a ship
OP: Yep - specifically I was thinking of the flags used to convey messages but well done :)
I help the seeking find,
Flag indicating something
OP: Yep, as in a flagged images on websites etc.
So many names that I can have,
there are many different flags
George and Jack spring to mind.
Union Jack St George's flag
OP: Well done :)
Not the iris in your eye,
Not sure about this one
OP: A 'flag' iris is a type of plant
Droop like the hangman's halter,
If there is no wind the flag will droop
OP: To flag can mean to droop or hang loosely
Walking me should be easy,
You can carry a flag around
OP: 'Flag Stones' are easy to walk on.
but know me best when you falter.
To flag is a synonym for to falter, with a connotation of fading.
OP: When you've been walking a while you'll begin to flag (get tired)