Pretty neat! Did she leap off the roof or was it the board?
That's Tillie and she was springing off the board. I don't think that you can command a Sim to walk or jump off the top of a building. In this case, Tillie was just standing at poolside, waiting for a command to 'get into the pool' via the diving board. You can also tell your Sim to get into the water by clicking onto those built in ladders.