I used to get the best watercress at the farmer's market but sadly the elderly farmer who grew it passed away.
Now, I can only find the stuff that's grown hydroponically. Sometimes it's called upland cress. It's rather spicy, which I don't mind, but it has a frail quality and limpness that the other didn't have.
Another farmer grows Thai watercress. Haven't tried that yet. I think it's also grown hydroponically.