In the next picture we can see two fins, one of rubber at the left (Hollis F1) and a plastic fin to the right (OMS Slipstream). Both have similar characteristics underwater with respect to thrust and control. The same is true for the ScubaPro Jet Fin (rubber) and DiveRite XT (plastic). Overall a good pair of fins must have the following characteristics:
- Wide blade.
- Rigid blade.
- Stainless steel spring to hold the fin to the heel.
- The size of the fin must be proportional to the size and strength of the leg of the diver.
The choice about using rubber or plastic fins must be based on the personal needs of the diver about balancing its scuba equipment in order to obtain an horizontal trim without too much effort.
As a general rule we can say that a diver requires rubber fins when there is no other possible adjustment in the scuba equipment and the diver is still with positively buoyant legs. More details of this we will see in the article about how to obtain an horizontal trim without effort.
There are stainless steel springs that are connected to the fin with a plastic buckle, this buckle is unnecessary and only adds a failure point to the system. We must also move away from plastic or rubber straps that ultimately always end up breaking.
A very common type of fin is the split fin. The biggest problem with this type of fin is its lack of control.
This type of fin is designed almost exclusively for the flutter kick, the consequence of this is that other types of kick like the back kick or the frog kick become extremely inefficient with this type of fins.
Fins which are generally designed to free us from the sensation of water resistance give us trouble when we need to stay still or we need to move backwards, in other words they affect our control underwater.
Apart from the problems of control, fins that lack of rigidity have an inefficient thrust, you might think that with a less rigid blade you will get less tired but in practice it is the contrary.
Consider for a moment on the fins used by athletes of free diving, in free diving is essential to move forward efficiently consuming the minimum amount of oxygen and producing the minimum amount of carbon dioxide. In free diving the fins used are rigid and in any case split fins are used.
The difference between scuba diving and free diving is that in scuba diving we need to have more control with the fins so these are not as long as in free diving.