Matthias Louvier (known as Matthieu Rouvier in the European version) was a professional diver and the co-founder of L&L Diving Service. He was the son of Jean-Eric Louvier and the father of Oceana Louvier. He died in an accident aboard a submarine while searching for the Pacifica Treasure.
Possibly born in France, like his father, Matthias grew to love the ocean he loved so much and spent all his free time diving. He never left his father's side and the two of them formed the diving service.
Sometime during his later life, he heard something that could've sounded like The Song of Dragons with Jean-Eric. Shortly afterwards, he heard rumors about a mysterious treasure left by the Okeonides and chased after it, despite Jean-Eric dismissing it as nothing more than tales and stuff and legend, and, therefore, breaking the two apart.
Matthias was one day in a submarine known as the HD-9 during research in the Zahhab Region Depths, when the engines failed and the air inside ran out. According to Jean-Eric, when the rescue team went down to the wreckage, no one was inside, implying that Matthias escaped and probably died, as he is never heard from again.
- Although most of the game establishes that Matthias is dead, there is a quest involving a diver who suffered from memory loss as the result of an accident, and the player character is required to photograph a few sea creatures to help him regain his memory. One of the final requests is a photo of Oceana, as he recalled having a daughter about her age. He is only refered to as "ML", and after completing the final request, Jean-Eric hints that "ML" is in fact Matthias Louvier, although the game never provides a clear confirmation or denial. Another hint is that in the European version, Matthias Louvier is called Matthieu Rouvier and "ML" is called "MR."
- It is possible that he was the one that saved the player and the others on the radio when the Cavern of the Gods was collapsing as well as the one who told the player to collect the coins.