With the exception of trick water skis, water skis generally have fins on the bottoms to make turning and maneuvering easier [source: Sports Authority]. If you're a beginner buying combo water skis, the fins aren't really a big issue to be concerned about. When they eventually wear out, you can buy a plastic replacement fin from an Internet retailer for less than $15 [source: Overtons.com].
When it comes to slalom skis, though, tinkering with the fin -- along with the bindings -- can make a big difference in performance. Moving the fin forward, for example, will make the ski feel smaller and turn faster, while moving it back will make the ski seem bigger and more stable. Adjusting the depth of the front of the fin in relation to the rear will also control the amount of pressure on the tip of the ski at the finish of a turn, which means the difference between overturning forward and doing the equivalent of popping a wheelie on a motorcycle. If your ski tends to slide out at the finish of a turn, adjust it to sit deeper in the water. Remember, we're talking tiny adjustments here -- try one-tenth of an inch at a time [source: Adjusting Your Slalom Ski].
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