This particular area of water contains vast amounts of WW2 wreckage and debris from numerous engagements, both air and sea.
That debris comprises large chunks of metal such as torpedoes, large shells, sea mines, and sizeable parts lost from ships that weren't sunk, but only badly damaged.
The Battle of the Java sea over 26-28th February 1942, was a huge battle between Japanese, American, Australian, British and Dutch warships that resulted in the loss of 6 known ships.
Another sea battle between the Japanese and U.S. and British ships on 1st March 1942 saw another 4 ships go to the bottom.
Then there are the numbers of WW2 aircraft losses in the Java Sea, both Japanese and Allied, from numerous dogfights, and just simple accident losses.
Add to that, civil wreckage such as ferries and local shipping lost over numerous decades.
The bottom line is, that this area is a recreational divers paradise, strewn with wreckage. Add in poor visibility in numerous areas caused by storms and strong currents, and you have wreckage search conditions that can best be described as "difficult".
Until a positively-identified section of the QZ8501 flight aircraft can be produced, there will be a large amount of "false alarms" produced in the wreckage search.
The fact that the current items reportedly found - that are immediately being identified as parts of QZ8501 - are listed as being found 100kms from the LRP, seems to me to be a somewhat unlikely location.
http://ibiblio.org/hyperwar/USN/USN-...-JavaSea-7.jpg