Marina is a Pokémon Trainer from the Orange Islands who is just as crazy about Water-typePokémon as Misty. Whilst traveling around the Orange Islands, she and her Tentacruel rescued Misty's Psyduck from drowning in the sea. After realising Misty was a water Pokémon trainer who also shared a fondness for water Pokémon they became fast friends although they had a Pokémon battle to determine who the best water Pokémon Trainer was.
Psyduck is Marina's Pokémon and because it is a water Pokémon, Marina is very fond of it.
Psyduck managed to defeat Misty's Staryu but was defeated by a Golduck that was taking orders off of Misty.