Hoping that they can find this black box but not looking good is it?
The usual way to find the CVR and FDR is to follow the pinger, but even in shallow water that can take several days as we saw last year with the a/c that hit the water on a handover flight.
Once the pinger battery packs it in, they will have to go to sidescan sonar. Given the irregular bottom profile and the likelihood that the section containing the CVR and FDR will be just one of many dispersed pieces, it's going to take a loooong time and a serious pile of megabucks.
But it's a doable.
Amazon.com: Ship of Gold in the Deep Blue Sea: Gary Kinder: Books documents the years of effort required to find a historic shipwreck on a flat seabottom.