While leveling the site and screening sand for the new cistern, we decided to increase the area and put up a swimming pool we've had in the shed.
Now that the barn tank is so full, it really isn't much good for the kids to swim in. Even though we have water to spare and we hate to see it being "thrown away" by not being collected, we have decided to keep the water level in the pool low. Now, either Leo or Nicky can fall down and will be safe (though still not left unattended!).
Leo actually helped with the whole process - levelling the site, screening and raking out sand, and putting the pool itself together. It was very cute to hear him tell Nicky, "I've been working all day and I'm very tired, so you'll have to be gentle with me!".
Both kids love it and want to spend as much time as possible in it.