The development of underwater biomimetic robots has recently become an active research topic due to their stealth, performance, and maneuverability. In this two-part paper, we present the system design and characterization of a multipurpose, miniature, bioinspired low-cost robotic fish implemented in a fun-science activity for pre-high school students at the New York Aquarium; the activity is aimed at igniting K-12 students' interest in science, technology, engineering, and mathematics (STEM) and to attract them toward engineering careers. The robot features a servomotor-actuated modular caudal fin for selection of swimming modality and thrust optimization. The thrust produced by various caudal fin geometries is experimentally quantified, reported, and discussed. In addition to its applications in K-12 education, this robotics platform is utilized for several robot-live fish interaction studies, where the effect of robot leadership in fish shoals is investigated.