A bio-inspired jet propulsion mechanism was designed and developed for development of proficient unmanned undersea vehicles (UUVs). The propulsion mechanism mimics that of the Sarsia sp. jellyfish which measures approximately 1 cm in diameter. In order to achieve a biomimetic uniform bell contraction, an electrical motor was used in conjunction with a novel circumferential actuator based upon a mechanical iris diaphragm. This mechanism allows actuation of a deformable cavity. The current prototype was scaled to a diameter 10 times larger than Sarsia measuring 10 cm in diameter. The performance of the propulsion mechanism was analyzed both experimentally theoretically. The prototype was mounted on a test stand which allowed for measurement of thrust and power consumption. Analytical and experimental results were compared to that of the performance of Sarsia. It was found that the overall mechanism created a maximum thrust of 5.1 N with a calculated vehicle efficiency of 0.17% and proficiency of 4.8 s-1.