Star fruit
Damasonium minus

It is perhaps best known as an agricultural weed. It is a major weed of Australian rice crops.
This species is an emergent aquatic plant. It is an annual or short-lived perennial herb growing up to a meter tall. The floating or emergent leaves have blades up to 10 centimeters long by 4 wide and lance-shaped to heart-shaped. They are borne on petioles up to 30 centimeters long. The branching inflorescence has whorls of flowers. Each flower has tiny green sepals and white or pink petals a few millimeters long. The star-shaped aggregate fruit is made up of follicles containing seeds.