Swimming to help exercise damaged muscles and tendons is called hydrotherapy.
It has worked to help smaller animals before, like cats.
But Samira the big cat will only be allowed to paddle in her lifejacket for a little while longer because she is now nine months old.
When she is fully grown, she will be two to three times as big, which could get dangerous in the pool.
Samira is one of the few Barbary lions left. They became extinct in the wild in the 1920s.
It's thought she is actually royalty too, descended from Barbary lions which were owned by the King of Morocco.