Benjamin is Marina Del Ray's sidekick, but he is much nicer than Marina, even complimenting Alana. He often follows Marina, trying to help her. He is later seen pampering her, showing he is either a friend or a hired servant. He puts up with Marina's rants, though it is clear he takes no interest in them. When Marina steals Sebastian's job, by busting him to King Triton, he is put in her place as the girls' helper. Unfortunately, on his first day of the job, Ariel runs away and Benjamin swims off to tell Marina. Marina is trying to win the King's approval, but he doesn't listen until Attina breaks the news to the King herself, though he did tell Triton that Sebastian is also gone (he, Flounder, and the Catfish Club members left with Ariel). Marina then begs him for the key to her electric eel's cage, but he refuses to give it to her, notifying that she told him never to give it to her, in a fit of rage. However, Marina distracts him with "pretty fishies" and steals the key, releasing her eels to hunt Sebastian and Ariel.
At the end of the movie, he is sitting with Marina in jail (apparently he has become her prisoner psychiatrist) and tells her "You can't just hurt people. Hurting is mean. We don't want to be mean, now do we?". She agrees, and they samba until the credits roll.