"Shimizu" is almost exclusively used as a surname (last name) in Japan, and it ranks as one of the many common, traditional family names across the archipelago. It is extremely rare for "Shimizu" to be used as a given name (first name) for an individual. Japanese naming conventions distinguish clearly between surnames, which are inherited and link individuals to their ancestral geographical roots, and given names, which are typically chosen for their auspicious meanings, pleasant sounds, or seasonal associations. Because "Shimizu" is so deeply established in Japanese culture as a topographical family name, using it as a first name would be highly unconventional and likely confusing in a Japanese social context. If you see the name "Shimizu," you can safely assume it is a family name, and it is almost certainly being used to identify an individual's lineage and heritage.