Unlike Sonic, Knuckles is able to swim. As is typical among Sonic characters, Knuckles can roll into a ball to attack enemies. He also has an empowered "super" form: using the Chaos Emeralds allows him to transform into Super Knuckles.
As for why Knuckles can swim, it is most likely because he is a strong swimmer and is not afraid of water like Sonic is.
In Sonic Mania, and its expansion Sonic Mania Plus, this maneuver is referred to as Swim and is usable to only Tails and Super Tails. Being the underwater equal of Fly, Tails swims around underwater using doggy paddle when performing Swim.
As if the great abilities of Knuckles the Echidna never end, another one of his trademark tricks is his gliding ability. Because he has those long dreadlocks, he can spread them out while he's in the air and they'll allow him to glide far distances.
Plus, that also means that when Sonic tries to fight back, he can quickly move in to land a punch before Knuckles can even react. So, sure, Knuckles may be the strong one when it comes to actual physical strength, but that doesn't mean Sonic is weak and can't still get a few good hits in before Knuckles can touch him.
Yet Shadow is the most powerful character because of his lab origins. Gerald crafted him very carefully and made him practically immortal, so he could carry out his mission of healing without any major obstacles. So while Shadow can be stopped, he cannot be physically defeated, which makes him the strongest character.
Super Knuckles
When Knuckles is in his Super State, he gains invincibility and all his powers and natural abilities are enhanced up to their full limit. Super Knuckles is several times faster and more powerful, and can climb walls twice as fast and fly. He however need rings to maintain this transformation.
Sonic Can't Swim Because Creator Yuji Naka Wanted Him To "Have Something He Is Not Good At As A Character" The character could probably walk on water with enough speed.
In the first games, knuckles ran at a little less speed then sonic, while as the series evolved he became an average runner running at about 15 miles an hour.
For sustained runs, Sonic clocks in at 767 miles per hour and his max speed reached is 186,000 miles per second, or in other words, the speed of light. Sonic can't sustain running at the speed of light, but he can regularly run faster than the speed of sound.
Tails is clearly the smartest person on this list, his a two tailed fox with a dangerously high IQ that matches Egg-man's perfect - but, Tails might become the smartest fox alive when his an adult or the smartest in the universe when his Egg-man's age.
Amy Rose. Amy Rose is a pink hedgehog and Sonic's self-proclaimed girlfriend, who is an energetic tomboy.
Fun Sonic Facts: Knuckles' weak point is girls. (He's very shy.)
Knuckles is a fictional red anthropomorphic echidna, the only living descendant of a well-established clan of echidnas. For many years, his clan guarded a giant gemstone called the Master Emerald, which controls the Chaos Emeralds, objects central to the Sonic the Hedgehog game series.
In fact, Knuckles turned super as soon as he started appearing in Sonic games. Players were able to play the game as Knuckles in Sonic & Knuckles. That meant when all seven Chaos Emeralds had been collected, just like Sonic in previous games, Knuckles was able to harness their power and turn super.
Sonic for the most part has pretty good stamina. His whole shtick is running for long periods of time during his adventures without getting tired. However, He does need to sleep.
It's that power that turns Sonic into Super Sonic. He turns a glorious golden color and can fly at nearly the speed of light.
Aquaphobia. Sonic is commonly considered to be afraid of water. Different media present the issue in different ways, from a mere cautious objection to going into the water to a crippling horror of H2O in all its forms. At the very least, Sonic cannot swim.
According to fans, Sega's rules state that Sonic can't "show excessive emotion", or even lose against the bad guys. All Sonic characters are also apparently barred from hooking up with one another, get new family members, or be killed off.
Sonic's only weakness is that he cannot swim, sinking like a rock if plunged to a deep body of water. The reason for this is because Yuji Naka had a misunderstanding about hedgehogs not being able to swim. The only exception is that he can swim in the Sonic the Hedgehog Adventure Gamebooks.
In the games, Knuckles does not have a girlfriend (although it's hinted that Rouge and Shade has a crush on him). However, in the Archie comics, Knuckles' girlfriend is Julie-Su.
As if that's not bad enough, Knuckles's original name was actually "Dreds," a reference to his dreadlocks. Seems like they made the wiser choice by naming him after those spikes poking out of his knuckles, though.
Silver is below Sonic. They are no where near Equals. In the games Sonic has bested Silver in nearly every fight. In generations which is post sonic runners sonic defeated Esp Silver which is Silvers true power and maximum potential.