They shouldn't work, it's as simple as that. A fin with a great gouge up the centre so the two halves of the blade flap about. You can't get any propulsion with fins like that. If your fins split you throw them away! The truth is however that they do work and work exceedingly well too.

At first appearance, the Bio-Fin looks to be very simply constructed and in many ways it is, yet many hours of design and re-design must have gone into making something this 'simple'. Take the fin strap for example - now there's not a lot you can say about a fin strap but the back of the Bio-Fin strap is formed into a large loop. Most other fins have some sort of tag arrangement for pulling the fins on which is neither use nor ornament. With this strap you stick your finger through the loop and pull the strap over your boot - simple. The strap is tightened by the usual ratchet fastening and is released by fastex style buckles. The idea behind the split in the fin is to channel the water flow in either direction and increase the thrust on both the upward and downward stage of a kick. The blade is supported by a thick rubber fluke that runs from the foot pocket to the tip. With a heavy rubber grade used throughout the fin it feels much heavier than most other fins yet this can work to your benefit as you shouldn't need to use ankle weights with the fins.

The major claims made about these fins are: increased speed, reduction in muscle fatigue, reduced air consumption and an ability to swim against strong currents. The weight of the fins on land disappears as soon as you hit the water, where your initial feeling is that the fins aren't there as you feel so little resistance against your fin strokes.

Over the past six months the fins have been used on a wide variety of dives in differing conditions including a gas dive when the tide that was slack on the surface was running like a train at depth and a shot line descended down at about 45º. I arrived down a good minute before other divers who had left the surface at the same time and wasn't short of breath.

We may not be looking for the increased speed that the fins allow you to achieve but I have found that as far as Apollo's other claims are concerned they are certainly justified. The only negative comment I heard about the fins was the price and £130 does seem steep for a pair of fins. However (although I can't prove it) I'm sure that by the number of good old rubber jetfins I see around that the Bio-Fin's flukes will keep on beating long after many a cheaper pair have split. For information contact Forward Diving on: 01202 677128

Review by Ron Mahoney