We have known for sometime now that the smoke monster is kept away by the use of sonic fences. Now we know that in the smoke form it can not cross water. I believe it was confirmed before that the smoke cannot separate itself from the ground and that is why it can not just fly over the fence. This is just a couple of the probably many limitations the smoke monster has when it is in that form. Now what I am wondering is if there is a reasonable scientific explanation behind what the smoke monster is/consists and of its limitations or is there a some other reason it can't do these certain things.
Scientific Theory: First we would have to consider what materials/objects can not pass through high frequency sonic waves. We know that humans can pass through the field but with disastrous results but the smoke can not even do that. One idea would be that the smoke is made up completely or partially of electromagnetic waves. Then perhaps when it comes in contact with these sonic waves, the waves of the smoke monster are annihilated or changed drastically. The idea that the monster can't lose contact with the ground could be because the islands electromagnetic energy is fueling it and the smoke has to stay "grounded" so to speak. As for not being able to cross water, it might go along with the smoke not being able to lose contact with the ground or it could be something like in Back to the Future when the hover board doesn't work on water. This is just one idea I had... I'd like to hear any other scientific ideas and any other ideas that would limit the smoke from passing the fence and moving over water.