Mares Quattro
Claim: Flexing center channels translate leg movement into
directional thrust, while the stiffening side rails increase the blade's
effectiveness for frog kicks and sculls. (Review in Sport Diver)
Finding: Channeling of water down the fin by troughs or rubber
channels (Quattro) does not appear to improve thrust or economy.
Scubapro Twin Jets
Claim: Proprietary drag-reducing vents and extended side plates
for increased leverage and power. (ad in Sport Diver)
Finding: The use of Venturis, or vents, either forward or rearward
facing, does not appear to improve thrust or economy. Water does
not pass through the vents, thus they do not relieve the negative
thrust in the recovery phase.
Apollo
Claim: Split fin design allows for more power and less effort than
any other fin. (Apollo's website: www.apollosportsusa.com/Biofin.html)
Finding: There was no difference in energy cost between the split
fin Apollo and the same model with the split taped closed, suggesting
that the split was ineffective in improving economy. The longitudinal
splits also do not appear to improve its thrust.