|Affiliations|| Ben Tennyson|
|Relatives||Donovan GrandSmith (grandfather)|
|Voice Actor||Kath Soucie|
|First Appearance||They Lurk Below|
Eddie GrandSmith is the grandson of Donovan GrandSmith, a wealthy resort chain CEO.
He looks a lot like his grandfather and even wears the same clothes as him. He has a dark maroon sweater with a brown turtleneck and white pants. He has black hair and blue eyes
Eddie tends to be arrogant at certain situations. When he first met Ben and Gwen he was rude and off-putting. After his grandfather convinced him to give a tour for them, he was saying that how good swimmer he is, causing Ben to mock him. He strongly dislikes how his family solves every problem with money. However, at the end of the episode, he became cheerful, told his grandfather to call him Eddie and hugged him.
Eddie was in the underwater resort when it was attacked by some robotic aliens. After seeing Ben Tennyson disappear and "suprisingly helpful aliens" appear, he began to guess Ben's secret. After being trapped with Ben and his cousin Gwen in a tunnel that was rapidly filling with water, Eddie finally guessed Ben's identity and revealed this. Eddie then traveled with Ben into a chamber with the Undersea Manta Ray, saw Ben transform into Upgrade and escaped via the upgraded sub.
- They Lurk Below (first appearance)
- He was called Edwin by his grandfather throughout the episode.