HOW IT WORKS...
BulletFins® riders report increased speed and drive from their boards and reaching planing speed more quickly.
What's going on? ....
The BulletFin's patent pending bulbous design is based on 50 years of experimental Naval Architecture and applied hydrodynamic research on the bulbous bow hull design. The bulbous bow is now the standard hull design for many types of ships.
Just as with the bow of a ship, the traditional surfboard fin creates a wave as it displaces the water in its path. The resulting turbulence places drag on the surfboard.
The bulb of the BulletFins® greatly reduces this drag by creating a new (primary) fin wave in front of the original (secondary) wave. This new bulb wave is designed to be nearly 180 degrees out of phase with the original fin wave to subtract its turbulence thus reducing fin drag.
The result is a fin that gets more efficient as you approach the surfboard's optimal hull planing speed.
Take a look here