What your dad saw was no coincidence. I can't tell you how many times I have caught several halibut making the exact same cast repeatedly after catching one fish. If you get a halibut, especially a good one, keep casting there at least 5 more times. The halibut move around a lot in schools certain times and you can really take advantage of that. Other times when they are less active, it seems like the bigger halibut will be solitary and sitting right next to kelp or eel grass. But when they decide to school up and move around, take advantage of it.