Knuckles the Echidna is the fifth boss in Sonic the Hedgehog Triple Trouble, who the player will face at underwater tunnel of Tidal Plant Zone Act 3. The battle is slightly different if the player has either Sonic or Tails.
In the battle, Knuckles challenges the player in an underwater battle, while the echidna himself controls the blue colored submarine mobile with small jet engines, and few weapon sets. The battle can be long, as the mobile takes 16 hits to be destroyed.
The battle at Tidal Plant Zone Act 3 is set entirely underwater, and as such, the player is susceptible to drowning. After breaking the Super Ring monitor, the player faces off with Knuckles, who is employing a strange submarine vehicle, as opposed to fighting the player one-on-one like he did last time. The battle takes place on a scrolling screen as Knuckles moves backwards, firing at the player. Knuckles attacks by throwing two bombs, that explode on impact to the ground. After this, Knuckles fires a homing torpedo toward the player.
When Knuckles repeats both attack types two times, he will rise off the screen at equal intervals to the surface to breathe; at the same time, an air bubble will conveniently rise from the ground, thus allowing the player to breathe. Knuckles then returns underwater and will repeat the same pattern again. If the player manages to do 16 hits, his mobile will explode and Knuckles falls off the screen.
When playing as Tails, he can use the Sea Fox for this battle, making the fight much easier, as it allows the player to attack Knuckles from a distance by shooting bombs into him. Knuckles has the same attack patterns and if he manages to hit the player enough, Tails will lose Sea Fox and has to continue the battle like Sonic does. While air bubbles aren't needed while using Sea Fox, they become useful after losing the submarine.
- The player can easily load the Spin Dash and attack quickly below the submarine mobile while doing three or four hits on total at one time.