“If there’s a boat on it, it’s navigable.”
That’s not entirely true. I worked for a CA company and we were discharging some clean cooling water from a press into a local creek. One day the Coast Guard showed up and asked us for our “discharge permit.” It seems that the creek flows into a non-navigable river, which, in turn, flows into San Francisco Bay ( sometimes). Since, at times water flows through this “collection,” the creek is, by definition, “navigable,” One of our engineers said we didn’t know because they hadn’t parked their Cutter out back! Someone should have put the Army Corps of Engineers out of business right after WWII. They are just an arm of the EPA.
Yeah - that’s the “significant nexus” aspect. But USACE doesn’t make the rules - congress does.