In the following tutorial, you can learn how to create custom pools.
Normally, you can only make square/rectangular shaped pools. But with a little trick, you can make them in all shapes you want. It may sound a bit complicated for the first time, but it will be very easy once you get the hang of it.
First, just lay down a normal pool:
Then, hold down CTRL and the left mouse-button, and drag your mouse where you want to add to the pool.
Now just release Ctrl and the mouse button. Click 1 more time and the poolsection will be added.
As you can see, the selected part has turned into a pool. You may add as many more parts to the pool as you wish. Occasionally, it may not be possible to add parts in certain places though.
c´est tuto pr les piscines en L dsl il est en anglais