I bought a pair of split fins on a cruise ship to snorkel the Caribbean for about $70 about 6 years ago. Don't remember the brand, but I'm a picky guy and when I bought it, it seemed to be decent quality. It was the biggest piece of garbage I ever owned. Easy to kick but NO power whatsoever. From that point on I wrote off split fins and considered them fins for the weak and the lame.
My dive buddy (and younger brother) started having problems with his ankle. Our LDS sold him a ScubaPro Twin Jet to help. A strange thing started happening during our dives, WE COULD NOT KEEP UP WITH HIM!!! During lobster dives in the keys we cover a lot of ground. He seemed to put very little effort and was sustaining high speeds for long periods of time. He outpaced us during long surface swims no matter what the current. I thought I was just getting old and fat. At some point I thought to myself, maybe its the split fins?? Based on my previous experience with split fins there was no way it could be the fins, I was in denial.
I borrowed his fins and did a series of tests to compare them against my Scubapro Jet Sport. I was shocked. Granted the Jet Sport is not the best fin in the world, but the Twin Jet split fin substantially outperformed my blade and required little to no effort. Not only was there a difference, there was a HUGE difference. When putting a leisurely, normal effort on my blades, it took me 45 seconds to get to the end of the pool. Using almost no effort on the Twin jets I reached the end in 35 seconds. On full power, I reached the end in about 20 seconds on both types, but the splits required way less effort. Using the blades I was completely exhausted and slowing down at the 80% mark. On the splits I maintained a constant speed and turned around and could do it again and again. I did all sorts of other tests including a couple runs holding a fin in front of me to create drag. The comparison made me realize how crappy my Jet Sport was. They felt awkward and unnatural in comparison to the Twin Jet. I also noticed that I "surge" when cruising on the blades. The lane tiles on the pool floor provide an excellent reference point. I was creating drag in between thrusts. On the splits I cruised on a consistent even pace, and felt no drag. Maybe I have bad technique, but the splits made it go away. Also noticed that the blades put a significant amount of strain/pressure on my knees. No strain on the splits.
After this test and being outpaced by my brother on every dive I was convinced. After doing more research I decided to buy the Apollo Bio Pro as it seemed to fare slightly better than the Twin Jets based on reviews, I wasn't crazy about the look of the Twin Jets, and I didn't like the large toe hole of the Twins as my foot would dig into it and pinch. Although I'm sure there are disadvantages to splits, for what I do the advantages clearly out weight the disadvantages.
What I also learned is that all splits are NOT created equal. I'm guessing split haters out there probably had a similar experience to mines. Many divers likely tried out the split design with a cheap fin before dropping 200 bucks on a quality one, and subsequently called BS to the design based on the cheap fin finding. Its a shame that cheap split fins likely ruined the reputation of quality split fins. Based on my first encounter with a split fin, I can see how a cheap split fin can be the cause of a boat getting smaller on a long surface swim and why it probably coined the term "death wings". Cheap blades would likely not have the same issue.
Either way, I'm a repentant split hater and love my new splits.
