From the released pair of pictures alone, the objects just look like whitecaps.
The reports from the Australian PM are that the objects looked "awash", which means there must be multiple sightings lurking unreleased showing a persistent object covered differently by water.
The released pictures were taken four days ago, so I'm sure the objects have been verified to be still there on several more images since, which is good news: and if the objects had been afloat for several days before being seen on 16th, and seen again since, then they're probably still on the surface now for when a ship arrives at the scene. 24m is far too big for a container, and probably an inverted yacht.
From the weather and measured drift in the images since 16th, the location of any sunk wreckage shouldn't be too uncertain. However, the water's substantially deeper here than where AF447 was found though, giving a submarine a harder time to find data recorder signals. For AF447 it did still take a long time to locate the wreckage on the seabed, despite finding surface debris more quickly in shallower water. I guess that experience will help this time.