Raft of Shags

Mother and I took our coffee down to the Inlet to enjoy and when we got there this flotilla of shags/cormorants were filling the bay.  There must have been over a thousand birds all bobbing down for food of bathing.  I have seen this phenomenon once before at the same location.  We watched them for over an hour then had to meet an appointment commitment.  A couple of hours later there was no hint of them. Why? & Where?