There would be gills and no fins. There would be a tail. It would look fat and round. They are also active swimmers.
Gills.
an adult frog has legs and a tadpole doesnt
At first they don't have any legs and then hind legs come out right where the tail starts. And later front legs come out behind their eyes. After that their tail starts to shrink and they become...
An adult tadpole is afrog so it eats bugs.