Why it takes so long to locate the recorders?
As others have explained, it is likely that the wreckage is in depths of water of about 1000M. You can't just send the local diver down in that kind of situation and it is unlikely that the technical equipment required to first of all locate the 'black boxes', and secondly to recover them, is close at hand. It will take time to get the equipment there by sea from the company or State 'contracted' to carry out the recovery.