When I was in Medford, Massachusetts, there was a pet store selling ground pines, obviously terrestrial and taken from the woods in the nearby Fells Reservation. I played dumb and asked where they came from and how well they grew in aquaria. I was told that they came from "some river in the Amazon", and that they grew very well in tanks. In Milwaukee, Wisconsin I saw a guy come into Aquatics Unlimited and try to sell them a bunch of common backyard weeds as aquatic plants. Fortunately, the staff knew their aquatic plants well enough not to be taken in by that.
I also wince when I hear someone come in and say, "Gimme some seaweed!"