Question: When do the fins activate?
About the article "Wakeboarding", section "Fins and placement".

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B. Gladiator has brilliant colors such as red, orange, yellow, beige, and white.
They have long fins, but in the wild, they have much shorter fins.
Domestic ones have flowing fins, while wild ones do not have them.
Wild ones are also not as colorful, usually green or brown, but they can show vibrant colors when scared, or the breeding season. 
The pectoral fins are normally held against the body, but when threatened the fins are expanded to startle potential predators which may include sea breams and mackerel.
The flying gurnard uses its pelvic fins to walk along the bottom of the ocean.
The oriental flying gurnard feeds on small bony fish, bivalves, and crustaceans. 
Foil shaped fins generate thrust when moved, the lift of the fin sets water or air in motion and pushes the fin in the opposite direction.
Aquatic animals get significant thrust by moving fins back and forth in water.
Often the tail fin is used, but some aquatic animals generate thrust from pectoral fins.
Fins can also generate thrust if they are rotated in air or water.
Turbines and propellers (and sometimes fans and pumps) use a number of rotating fins, also called foils, wings, arms or blades.
Propellers use the fins to translate torquing force to lateral thrust, thus propelling an aircraft or ship.
Turbines work in reverse, using the lift of the blades to generate torque and power from moving gases or water.
Cavitation can be a problem with high power applications, resulting in damage to propellers or turbines, as well as noise and loss of power.
Cavitation occurs when negative pressure causes bubbles (cavities) to form in a liquid, which then promptly and violently collapse.
It can cause significant damage and wear.
Cavitation damage can also occur to the tail fins of powerful swimming marine animals, such as dolphins and tuna.
Cavitation is more likely to occur near the surface of the ocean, where the ambient water pressure is relatively low.
Even if they have the power to swim faster, dolphins may have to restrict their speed because collapsing cavitation bubbles on their tail are too painful.
Cavitation also slows tuna, but for a different reason.
Unlike dolphins, these fish do not feel the bubbles, because they have bony fins without nerve endings.
Nevertheless, they cannot swim faster because the cavitation bubbles create a vapor film around their fins that limits their speed.
Lesions have been found on tuna that are consistent with cavitation damage.
Scombrid fishes (tuna, mackerel and bonito) are particularly high-performance swimmers.
Along the margin at the rear of their bodies is a line of small rayless, non-retractable fins, known as finlets.
There has been much speculation about the function of these finlets.
Research done in 2000 and 2001 by Nauen and Lauder indicated that "the finlets have a hydrodynamic effect on local flow during steady swimming" and that "the most posterior finlet is oriented to redirect flow into the developing tail vortex, which may increase thrust produced by the tail of swimming mackerel".
Fish use multiple fins, so it is possible that a given fin can have a hydrodynamic interaction with another fin.
In particular, the fins immediately upstream of the caudal (tail) fin may be proximate fins that can directly affect the flow dynamics at the caudal fin.
In 2011, researchers using volumetric imaging techniques were able to generate "the first instantaneous three-dimensional views of wake structures as they are produced by freely swimming fishes".
They found that "continuous tail beats resulted in the formation of a linked chain of vortex rings" and that "the dorsal and anal fin wakes are rapidly entrained by the caudal fin wake, approximately within the timeframe of a subsequent tail beat". 
Its color is typically a scarlet red with silvery undersides.
It has a black crescent-shape mark at the base of its pectoral fins.
The fins are yellow to orange.
This species can reach a length of TL though most do not exceed .
The greatest known weight for this species is . 
Fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling the horny keratin in hair and feathers.
Most sharks have eight fins.
Sharks can only drift away from objects directly in front of them because their fins do not allow them to move in the tail-first direction.