lore dump:

he gotten the robot limbs thanks to eggman in exchange to fight sonic but eventually switches sides and now gets new limbs from tails!

his special ability (besides swimming and diving better than the rest of sonic cast or breathing underwater) is exhaling, while he holds his breath he just slightly floats like a balloon, and then stops after you do nothing for a long enough time or you choose a direction for him to blow himself over!

as for super form, his robotic limbs just act like flikkies when tails gets the super form, meanwhile swimming in air and all that. also a lil neat detail is that his 2 dots on corner of his eyes turn to star shapes when super!

bonus fact: his jumps are slower than the rest of sonic cast.