I cant say for sure but these fish may have been leopard sharks. Lately there have been alot of them cruising around in the shallows and if you run your swimbait over their back you can snag them. Alot of times if you put any pressure on them the hook pops out. If they where halibut its just bad luck. My only advice is dont swing right away, reel tight into the fish and let them turn a little away from you and then swing. Good luck.
PS. was that AM or PM
Daniel