Fast fish are not as uncommon as you'd think, as their little bodies wind their way through the depths of the ocean. What are the fastest fish in the world, though, and what makes them so speedy?

When going for your morning run, you'd expect to be moving faster than most fish can move through their environment.

You would think, at least, that the Ferrari that just drove past you in an extraordinary display of arrogance and narcissism was moving faster than most fish.

Yet, in some cases, you'd be wrong.

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The animal world record holder for fastest fish is an extraordinary creature, and a sea animal well worth studying.

There are two contenders which are commonly considered the fastest fish in the world: The bluefin tuna and the sailfish. While both are extremely speedy, one can sustain its speed for longer while the other has a more rapid acceleration and is capable of reaching quite remarkable g-forces as they whiz through the depths of our oceans.

Even the Guinness World Records cannot make a definitive decision when it comes to the fastest fish in the world, leading them to drop an article in 2015 announcing that both species would jointly hold the accolade. In the piece, they cite the fact that it is "notoriously difficult to obtain accurate measurements under natural conditions."

As such, we are going to present the case for both fish to receive the world record for being the speediest flippers in the ocean. What's the fastest fish? Well, it's complicated...

The notorious bluefin tuna might be suffering out there in the wild, but it's not due to any lack of speed. A 2015 study by the Large Pelagics Research Center in Massachusetts used a tracking device to look at the speed at which these extraordinary fish move, and managed to record a truly remarkable rate of acceleration in a specimen near Port Mouton in Nova Scotia, Canada.

What the scientists found is that the bluefin tuna managed to reach an acceleration of 3.27 g-forces (g), the equivalent of 144 miles per hour (mph) if sustained for two seconds. The problem, though, is that while this does push them way past the speed of the sailfish, it is never actually sustained for that long.

Instead, the research finds that the bluefin tuna does have a much more rapid acceleration, but because it only exhibits this acceleration during extremely brief bursts of less than a second, it is uncertain whether it could actually be classified as the fastest fish in the world. Still, the potential for 144 mph is not something to turn your nose up at.

In comparison to the bluefin tuna, the sailfish has a much slower acceleration, of about 1.79g, approximately 78 mph. The difference, though, is that there is far more evidence to suggest that these fish commonly travel at high speeds and are capable of remarkable feats of speed and agility in the water.

A trial carried out early in the 20th century and cited by Guinness World Records suggests that a sailfish managed to take out 300 feet of line in only three seconds. This would give it a generous velocity of 67.7 mph, sustainable over long distances and a far longer period of time as well.

The problem is that the speed trial, which took place at the Long Key Fishing Camp in Florida, didn't provide any concrete evidence, and it is not even clear what the exact date of the trial was.

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This means that while the records are there, Guinness World Records didn't have enough data to truly determine whether its recorded speeds were legitimate.

This is ultimately why this record is still yet to be confirmed – there is not enough concrete evidence for either the bluefin tuna or the sailfish. What can be said, though, is that the world's fastest fish is almost certainly one of the two.

Whether the sailfish or the bluefin tuna is the fastest fish is of course still up for debate. What we can agree on, though, is that these are some ridiculously speedy fish!