What about pools?
Refreshing during the summer heat, never ending source of fun for kids (and adults alike, to be honest...), they involve a lot of precise and attentive work to be a safe and pleasant experience.
During the years we developed a deep knowledge of the chemistry - I like to call it witchcraft - that governs pool waters. A fine balance between sanitising agents (chlorine or oxygen), pH reducers, alkalinity correctors, anti-algae and many more, is a difficult thing to obtain. If not carefully maintained and checked regularly, chemicals byproducts can pile up in the water and render it less pleasant to dive in, with bad smells, growth of insects and algae and potential damage to the filter and pool liner.
So there you have it, under a quiet, soothing movement of the water surface in your pool lies constant care, knowledge of the products and how to use them.
For a clean and healthy pool there is no such thing as “just add SOME of THAT product”.