No its too small and an umbrella wouldn't fit as the pool shed is a couple feet behind it. Another guy speculated it could be to drain water that could collect around the outside of the pool if the liner leaked or to check for leaks
Does anyone know what this tiny plug could be for in the bottom of the picture? The skimmer is in the middle with a rock on it. This is an inground pool in southern Ontario, the small plug in inline with my pool shed