Some of the comments on beacons above seem to be rather confusing.
My understanding is that fixed beacons will only work if not submerged. So in the cases above a submerged fixed or deployable beacon beacon would not operate.
This was why deployable beacons were developed so that the crash site could be pinpointed by tracking the floating beacon.
If you want to find the sunken wreckage you need an accoustic beacon. Fitted as standard to CVFDR's and often fitted as a stand alone item on offshore going aircraft. This is water activated and does not use radio signals.
If this is inacurate I am happy to be corrected!!!