Pine cones contained by sea? Does anyone know how long pine cones will last if submerged surrounded...

Does anyone know how long pine cones will last if submerged surrounded by water? I am going to variety a center piece for a wedding and I want to use pine cones within the bottom of the vase.
Thanks
Does anyone own an indoor herb garden?
Answers:    pine cones will final indefinitely in river.
BUT- they will close up and won't look a thing approaching they do when they are dry.
AND- they can discolor the water....brown.
SO- you may want to rethink this.
Is it evil to put to death birds...
I would purely experiment now by submerging one yourself and see how long it last.