The fences that are legal for pools here are meant to be very difficult to climb like
these ones. They basically isolate the pool from the rest of the yard. Worth putting in if you have a small child even if they're not required by law in your area.
If your back door opens straight onto the pool, best to get self closing doors to protect the little one. Even when she can swim, it's sometimes hard for little kids to actually get out of pools, particularly if they're fallen in and used up lots of energy trying to get to the side after a big fright.