Lots of concentration on the civilian ships (and ADV) searching for some wreckage, how about any submarines ?
The RN sent a nuclear sub - no updates as to where she might be.
The Australians have some ( 4 ????? ) Collins class submarines which were subject to a very acrimonious procurement process - here there has been no mention of their deployment.
And, of course, the US has a few subs knocking around.
Submarines have extremely sophisticated underwater listening equipment and the lack of publicity is odd.