He started drawing manga when he was in elementary school. After graduating from junior high school, he helped his family business fish shop for three years. In 1958, when he was 18 years old, he posted his debut work "Shinya no Kyaku” to the newcomer manga contest of the manga magazine Kage under publishing company Hinomaru Bunko in Osaka. SATO Masaaki, who was one of the judges, evaluated his talent and strongly insisted on being selected, and he was awarded the runner-up. After that he lived in YAMADA Hidezo’s house the owner of Hinomaru Bunko, and wrote kashihon manga while also working as an editor. In 1964, he moved to Tokyo and published many works in Weekly Shonen King, in 1969 he started writing Ace no Jouken a full-fledged baseball manga. In 1970, he expanded his work to Weekly Shonen Sunday and Weekly Shonen Champion, serializing his first big hits Otoko Doahou Koushien and Zenikko. From 1972, he started Yakyuukyou no Uta and Dokaben. From 1973, he also wrote seinen manga with Abu-san, it was 41 years long serialization and completed in 2014.
In 2007, to commemorate the 50th anniversary of Mizushima as a mangaka, Dokaben - Superstars Hen was on the cover of Weekly Shonen Champion and contain appreciation message from FUJIKO Fujio A, SAITO Takao, TAKAHASHI Yoichi, ADACHI Mitsuru, TAKAHASHI Rumiko, MORIKAWA Joji, MITSUDA Takuya, INOUE Takehiko and TAKAHASHI Hiroshi.
On December 1, 2020, he announced that he would retire from 63 years of writing manga. His final work, a one-shot of Abu-san was released in August 2018.
He passed away at a hospital in Tokyo on January 10, 2022 due to pneumonia at the age of 82.
Infamous for being a big baseball lover, he presided two amateur baseball teams, Abu-san and Bots. When he was young, he tried to form a baseball team with his relatives, but there were not enough people, and he asked MOTOMIYA Hiroshi to join. He also once criticized Adachi Mitsuru’s works like Touch and others as "treating baseball as a romance prop.”
Mizushima was appointed as the first director of the Ishinomori Manga Museum. He took the Abu-san team and held an exhibition game in Ishinomaki.
Among his former assistants there are Motomiya Hiroshi, HIJIRI Hideo and IGARASHI Kokichi.
