I kicked and swam with these fins on, and I like 'em! They are a little softer than other brands I have tried and they come in a variety of sizes, and with the wide selection and softer material - they fit well. They are the most comfortable pair of short blade style flippers I have ever worn, and the comfort does not compromise their performance. Don Feil of Hydro furnished more information on the Finz:

Hydro is the exclusive North American distributor for Hydrosportz, an Australian company founded by Don McCredie, a former Australian National Body Surfing Champion. Hydrosportz has a surf division with body boarding and body surfing products and a swim division with a full range of swim products. McCredie developed and patented the concept of the split rail for his body surfing/body boarding Tech Fin with the idea that it would provide a grip in the water and allow rapid acceleration – critical when you only have one or two strokes to catch a wave.
 
He transferred the split rail concept to Hydro Training Finz and discovered that besides providing rapid acceleration, it also helped maintain the shape of the blade and contributed to even thrust in both directions of the kick. Hydro Training Finz are soft, flexible and comfortable. This is the first comment made by swimmers after their initial use. The fins have a greater surface area providing powerful thrust in both directions. The split rail (V channel edge) provides added surface area, allows the fin to grip the water for rapid acceleration, and acts as an “I” beam to maintain the shape of the blade. The split rail, the dimple at the end of the blade, and the downward angle of the blade all contribute to even thrust in both directions of kick. The extensive non-skid pattern on the bottom also adds to this resistance as well providing good footing for those odd ducks that insist on walking around on deck with their fins on.
 
Hydro Training Finz have been in team use in the United States for three years and three months with no reports of tearing at the toe pocket or splitting at the heel. The foot pocket allows minimal extension of the foot and the heel is extra sturdy to resist tearing. One team, Tempe Rio Salado in Mesa, AZ, has been using Hydro fins for more than three years at an outdoor pool. The coach, Michelle Bernal-Storjohan, reports no failures or fading, testimony to the high quality of material and resistance to ultraviolet light.
 
Initially, fitness and competitive swimmers were using long fins as a training aid. Because the center of effort is forward of the foot, the excessive blade area and displaced center of effort may cause early fatigue or cramping, and encourage a “pedaling” motion different than that used in a flutter kick. The concept of the short fin was conceived to bring the center of effort back to the foot, increase leg strength, and achieve the elevated race position, with a kicking motion specific to the flutter kick.

Hydro Training Finz are available in four two toned colors with no color relationship to size or stiffness. These "Finz" are built to last. The foot pocket design allows minimal protrusion of the toes reducing the possibility of tearing at the toe pocket.  The high quality and sturdy construction prevent splitting at the heel and deterioration from ultraviolet light. I highly recommend them. Hydro can be reached at (949) 646-8611.