Abstract: A jellyfish type underwater swimming toy capable of exhibiting reality sufficient to permit an observer to be impressed as if a jellyfish swims in a fluttering manner under water. A toy body is formed into a jellyfish-like shape and includes a head. The head includes a head body, a plurality of swing arms radially arranged on a periphery of the head body in a manner to be vertically swingable, and an umbrella-like member formed into a configuration like a thin film and arranged on the head body and swing arms. Thus, when the swing arms are swingably moved through a drive mechanism, the umbrella-like member is vertically actuated through the swing arms, resulting in the toy swimming in the water while vertically traveling in a fluttering manner.