You may mistake my post for suggesting Nessie doesn't exist. All I am getting at is, if there's a large animal the size of a whale migrating down to the loch,

You may mistake my post for suggesting Nessie doesn't exist. All I am getting at is, if there's a large animal the size of a whale migrating down to the loch, over a few hundred migrations since the weir was built, someone probably would have seen it. Therefore, the migrations, if they happen, most likely are a rarer event. On the flip side, the existence of porpoises, while interesting, does not prove the existence of Nessie. It simply makes more room for the possibility.