Yeah: water and oxygen are needed for life visible to the naked eye as we know it, but even more so, I would say, microbes are needed for life visible to the naked eye in whatever form. For if life exists, there's no other way we know of that it could be created except by evolution by natural selection, and evolution could hardly start off from large animals visible to the naked eye! And so, a microscope is probably the best tool to look for life.