Enzymes break down the organic waste into carbon dioxide and water.
Suntan lotion, oils and organic matter float in the water, collect dirt and then deposit onto the walls and other surfaces such as the filter. The scum line or bath tub ring in a pool or spa is a visual occurrence of this. The enzyme will collect this oil and be lifted off the wall. A surfactant in the enzyme product or algaecide used in the pool will help in this process. A physical advantage of this would be the feel of "softer" water. Another advantage is that the scum line will be removed without laborious scrubbing and if enzymes are added on a regular basis another scum line will not form. This means less work which is always appreciated.
If you can see the scum line being removed just think of how well it works where you don't see, like the filter and plumbing. This cleaning action of the enzyme in the filter will keep the filters from having to be manually cleaned as much, and again less work. Also this allows the filters to work better for longer periods of time between needed backwash or manual cleaning, giving you a cleaner pool. Using enzymes help to prohibit biofilms from establishing and adhearing to the pool surfaces. Also, you will consume less chemicals as the enzymes destroy some of the inorganic matter that usually will consume sanitizer and algaecide. Enzymes also help to clear up a cloudy pool by destroying the waste that may be too small to be filtered. Enzymes are not a clarifier and do not cause smaller particles to form larger particles for quicker filter removal.