The transition from aquatic to terrestrial lifestyle provides anurans the opportunity to occupy different ecological niches. The direct developing Microhylidae are a speciose family of frogs that has diversified ecologically into five ecomorphs: terrestrial, arboreal, scansorial, fossorial, and secondarily aquatic. The adaptive radiation of the microhylid family provides an opportunity to test the relationship between form and function in a highly specialized Anuran body plan. Six species, representing all five ecomorphs, were collected in Papua New Guinea and filmed in the field swimming at 30 fps. We quantified the hindlimb kinematics and calculated hydrodynamic force production to compare swimming performance in the six species. We hypothesized that the secondarily aquatic ecomorph (Austrochaperina palmipes) would swim faster, stronger and more efficiently than the terrestrial ecomorphs, even though it arose from a fully terrestrial ancestor. Center of mass velocity, stroke displacement, and swimming efficiency, as measured by the foot slip, were all significantly higher in the aquatic ecomorph. However, a terrestrial ecomorph (Mantophryne lateralis) had significantly larger propulsive impulse than the aquatic ecomorph. Additionally, of the terrestrial ecomorphs, the jumpers performed better than the arboreal, scansorial, and fossorial ecomorphs in terms of COM velocity, propulsive impulse, effective foot velocity, and stroke displacement. These results support the hypothesis that adaptation to ecological niches is driving performance.