The Attack’s more flexible sister fin, the Mares Quattro, produced slightly less velocity and distance per kick. But the Quattro outpaced both split fin models in distance per kick (that may be why the British magazine Diver rated the Quattro superior to the Apollo, based on subjective field tests reported in the August Undercurrent.) Between the two split fin models, the Scubapro Twin Jet provided significantly more distance per kick than the Apollo, which scored well below average in this measure. In fact, the taped Apollos outdistanced the split version. The researchers say that “The notion that rigid fins develop more thrust and speed was not supported by this study. The maximal velocity and thrust were developed by both rigid (Attack) and flexible (Apollo) fins, with the limitation of the rigid fins being the ability of the diver to generate a high frequency kick and the limitation of the flexible fins being the diver’s maximal leg kick frequency.”