This is a Young Plant. The leaves look much different as it ages, I lost mine & want to get another but my name tag is faded & I can't remember name, It requires lots of water & is often used in the edge of ponds.
After much searching I found the name of the plant. CYRTOSPERMA JOHNSTONII
I found it at a Florida Nursery & ordered 2. Stems get very rough as it matures. I Love it. If you Google there are many pictures.