ANTI-SILTING TECHNIQUES

Split fins are great for caves and wrecks. The reduced angle of attack of the split blades produces less turbulence than flat paddle blades to cause less silt-up. Of course, it is best to keep any type of fin away from the bottom and also not to kick towards the bottom to move away from it. Skilfull boyancy adjustment with the power inflator along with minimal fin movements allow excellent progress with reduced or even eliminated silt-up. In addition to doing the frog kick, you can also use a modified flutter cave/wreck kick, which is a VERY small range flutter kick (mostly ankles and a little knee) while the fins are kept away from the bottom. Also, because split fins produce excellent propulsion with minimal leg motion, you can skillfully reduce the occurrence of vortex shedding caused by large leg motions and wide fin movements.

The best policy in cave and wreck diving is thinking first before sweeping the legs around or kicking in any particular direction. I notice that when I am on a boat dive to a wreck, many divers are not careful or thoughtful about their leg and fin movements in enclosed environments. Their silt-up is more due to kicking and maneuvering as is they were in the wide blue open, like a bull in a china shop. For this reason, I first use the speed of the fins to get to the wreck first and be the first in. Then I take it slow, refine my technique and I do not stir up one piece of silt. When I look behind me, I see the next few divers entering the wreck and immediately I see clouds of silt kicked up by one or two divers (or more) who are not thinking about the ramifications of their next leg motion and that area of the wreck not worth returning to during that dive.

Silt-up is more a function of refinement of skillful finning techniques, positioning, body alignment and thinking. This includes proper weighting so that there is not so much extra weight on the belt that extra air needs to be added to the BC and the resulting torque tilts the legs toward the ground and the torso above the legs. This can cause the thrust of the fins to be directed at an angle toward the bottom rather than behind. In cave and wreck environments with any fin, it is best to be parallel to the bottom or even have the legs elevated slightly. When adusting leg or body positioning, it is better to use small repetitive gentle strokes rather than large sweeping leg motions which direct large amounts of water toward the bottom.

I have seen many divers kick toward the bottom in order to get off the bottom or farther away from the bottom. They did not think before acting to realize this will send a blast of water toward the bottom! Some of them continue to do this after the first time. Many do not look down at their fins occasionally to monitor their positioning, range of kick, or the effect they are creating on the bottom.

One thing I do to continue to refine my technique outside of caves and wrecks prior to entering them is to look back at my feet as I kick and be very aware of the kicking range I am using and how I can best minimize it. I also refine and adjust my body alignment as well so that my feet are not angled toward the bottom. This is good to experiment with above silty areas in open water. By looking back and monitoring your fin motions, body positioning and using gentle conservative maneuvering motions, you can gain a mental picture of what you are "feeling", and you can greatly refine and control your technique. I often use a toe kick version of a modified flutter.

I also notice that some divers use wide sweeping leg motions, and hard ones at that, to maneuver while in a cave or wreck just as if they were not in an overhead environment that is prone to silt-up. This can send off vortexes toward the ground, walls and ceilings. I have found that smaller, gentler repetitive maneuvering motions allow fine tune adjustment in position, avoid over steering and allow silt up to be skilfully avoided. Split fins are exceptionally good for fine tuned maneuvering using small gentle repetitive strokes that are executed with reduced silt-up in mind.

It's all in the preparation and thinking before acting.

The stiffer versions of split fins work great if extra "feel", "bite" or "torque" is desired. The more flexible version can take some acclimation time to refine the technique, but this can be well worth the time invested if the feeling of no fins at all is desired.