That’s really good news and a tremendous achievement considering the depth at which it was retrieved. I believe the signal only lasts for about a month, so they would have been searching almost or probably in the dark.

EDIT. Looking further at the discovery, it would seem that the U.S. discovered the location of the two black boxes last January but they have only just been retrieved.

http://www.abc.net.au/news/stories/2007/01/25/1833995.htm