Atlantis: the Lost Empire (2001)

It's the year 1914 and nerdish linguist Milo Thatcher has just received a treasured copy of "The Shepherd's Journal", a guide to finding the lost city of Atlantis from the wealthy Preston B. Whitmore, a friend of Milo's late explorer grandfather, Once Milo cracks the highly undecipherable language of the Atlantean people, Whitmore hires Commander Rourke and the beautiful Helga to lead a submarine expedition to find the legendary submerged civilization. However finding the city is only half the battle. Once they arrive in Atlantis, they must contend with an ancient king out to protect the land's mysterious crystal power source as well as his beautiful daughter, Princess Kida, from the unknown intentions of their new visitors.