That one will be Nymphoides indica, it's a native here along with other yellow as well as white flowering Nymphoides. N. cristata doesn't have the frilly edges to the petals. The flowers come from near the base of the leaf. If that comes in contact with soil (as when water levels drop) roots will emerge from there as well. While floating new leaves will come out from there and multiply across the surface of the water. A leaf will usually produce a flower at a time, but there are many buds under water waiting their turn.