I personally am not a fan of Gizmos. You are relying on that to act as a plug and an ice breaker. I have heard of them splitting and thus rendering the plug effect useless.
I plug via a traditional plug and then use an empty quart bottle filled partially with small stones to give some weight to sumberge half way in the water. This way if the bottle breaks, I only have some stones to suck up, but my plug is still in tact.