So I found this piece of driftwoodand I’d like to add it to the tank but it just won’t absorb water or sink. Had it tied to a 6+lb rock to hold it down but after 2 weeks it popped right back up. I mean it’s gotlike a waterproof center. Found it on the beach (salt water) months ago. Tried sinking it twice with no luck. Any body have an idea what to do to sink it?