The Bluefin has certainly had its share of challenges in its search for Flight 370. Its first two dives were cut short due to technical problems. So far, there has been no sign of the missing jet.
There are questions as to whether the Bluefin-21 can dive deep enough, and whether it can send back pictures that are clear enough.
So is there anything out there that can do the job better?
Rosa Flores has the story.
The autonomous underwater vehicle Bluefin-21 - said to be the search's best hope for finding Malaysia Airlines Flight 370 - has aborted it's first mission and returned to the surface of the Indian Ocean.
The mission was supposed to take 24 hours to map the first portion of the search area: 16 hours to map, four hours' of travel time to the ocean floor and back, and four hours to analyze the data gathered.
In an interview with CNN's Erin Burnett, Captain Mark Matthews, who heads the U.S. presence in the search effort, explains why the underwater robot returned to the surface earlier than planned.
Officials tell CNN there have been no confirmed acoustic detections over the past 24 hours.
That's significant because at most, the black boxes have a couple more days of battery life left in them, according to he largest manufacturer of black box pingers.
The technology that will search underwater for the wreckage - like the Bluefin 21 - is now of even greater importance.
CNN'S Rosa Flores has a demonstration on the underwater technology that will locate the missing wreckage.
Officials are zeroing in on what may be the missing malaysian airliner and have cut the size of the search zone after officials identified two more sets of pings that may be coming from Flight 370's black boxes.
With the latest developments - searchers could be just days away from taking the hunt to the next level with an underwater drone.
Our Rosa Flores has a first look at what the search may look like.
What if the passengers of Flight 370 tried to send messages before the plane went missing?
That's a crucial question not only for family members of the passengers, but for investigators who want to know what happened in the flight's final moments.
If and when the plane is found, forensic experts say personal cell phones and electronics may be the key to solving one of the biggest aviation mysteries in history.
Our Ted Rowlands is Outfront with the story.