Need a winter cover. There are a few different kinds for pools whether you have an in ground pool or above ground.
The easiest way to understand is by a picture therefore see below:
Tarp above ground cover with leaf net to aid in making opening the pool much easier.
Ultimate Above Ground Cover which allows the water to run off. Doesn’t blow up in the wind like tarp style covers do.
In ground tarp cover with left net and water bags
Safety Cover for in ground pools. Keeps you safe, looks awesome during the winter months, allows water to melt into the pool therefore avoids costly spring water top ups, and most importantly keeps your children and pets safe!