"Swampert is very strong. It has enough power to easily drag a boulder weighing more than a ton. This Pokémon also has powerful vision that lets it see even in murky water. It predicts storms by sensing subtle differences in the sounds of waves and tidal winds with its fins. If a storm is approaching, it piles up boulders to protect itself."
"When Swampert Mega Evolves into Mega Swampert, the strength that it needs to act in the water is increased, and it can use its tenacious power both on land and in the water. The musculature of Mega Swampert’s upper body has developed immensely, making it look tougher than ever."
Swampert first appeared as a Mudkip in The Search Begins! when he was given to Lexi by Professor Birch as her Starter Pokémon in Hoenn, after the other two Starters were given to May and Brendan. He is extremely cheerful and loving, and instantly formed a bond with Lexi. He remained outside his Pokéball, leaving him the ability to experienced the adventure first hand. He was very enthralled when Lexi would battle, even when he wasn't used.
Mudkip continued to be used regularly in battle, showing a growth of strength and willingness to become stronger. In Breaking News!, when the group was heading to Fallarbor Town, TV crew members Gabby & Ty were attacked by a group of Pokémon, enraged from the ongoing plans by Team Aqua at Mt. Chimney (although the group didn't know this at the time). Mudkip helped the best he could to stop the Pokémon, but wasn't strong enough. It was here when he pushed himself to the point of evolution, evolving into Marshtomp, and successfully halting the Pokémon from causing the group any harm.
Marshtomp continued to grow at time progressed. After an incident with Team Aqua at the Weather Institute, Marshtomp began to train heavily with Lexi, evolving into Swampert soon after the group left Fortree City.
As a Mudkip, he was an extremely loyal Pokémon and felt safer around strangers. During its travels with Lexi, it was shown to be more of a sensible type and assisted in breaking up and resolving arguments between the other Pokémon. It is also friendly with younger Pokémon. When Mudkip evolved into Marshtomp it retained the same personality but also developed somewhat of a edgier side. As a Swampert, his fierceness grew and became quite intimidating. However, he began to control this in order to retain it's approachability and caring nature towards others.
Swampert is very strong; He has enough power to easily drag a boulder weighing more than a ton. He also has powerful vision that allows him to see even in murky water. He can sense storms by sensing subtle differences jin the sounds of waves and tidal winds with his fins.