Swimming near Brussels

My wife and I like to swim every day for fitness. We currently live in southern California and have a pool in our back yard. We will be moving to Belgium to live later this year but we can't seem to find a place to rent that has a pool. We would like a place south of Brussels, around Nivelles.
What is the likelihood of us finding a place to rent that has a pool?
Are there public pools in that area?
Do gyms have pools we could use?
Any other advice?