Submerged plants can help make dirty lakes clearer. Scientists studied 19 lakes in China to see how many plant species are needed for this. They found that having three or more plant species can make the water clearer. The plants also help improve water quality. Two specific plant species, Myriophyllum spicatum and Vallisneria natans, are good for restoring these plants in lakes. The more plant species there are, the better the lake can become.