It is watercress, and, since it is quite a common plant, and since I have never heard of it being grown submersed in aquaria, I would think it would be quite difficult. There is no harm in trying, howver.
well it is growing a little bit. I am going to try for a while longer a week or two. where I found it it was growing submersed and had been there for a while. The water where I found it was a stream lots of flow and low temperatures. I am trying to grow this one at room temp. Do you have any reason to believe that it will be necessary to lower the temp more that that?