Do not read this if you have not yet seen the movie and are planning to.
I really love this movie. The central theme of the movie, IMHO, is: sometimes, a passion for something is so powerful, one has no choice but to forsake all other things in pursuit of this passion.
Jean-Marc Barr's character, Jacques Mayol, has such a deep passion for the sea, that he cannot share his life with Johanna. He tries. He really loves her, but his life is in the water. She eventually comes to understand this and delivers the most beautiful line in the movie, when she sends him to the bottom of the sea: "Go and see, my love."
In parrallel to this, Jean Reno's character, Enzo Molinari's passion is for the competition of free diving. He is World Champion, but he knows that somewhere out there, the little Frenchman, Jacques Mayol is better than him. Enzo is passionate about beating Mayol in the competiton.
Both of their passions run so deep that they have to forsake their lives in the pursuit thereof. Depending on the version of the movie you watch, of course. If you watch the American version, the whole point of the movie is trivialised when the dolphin carries Jacques back up to the surface at the end. Jacque's passion for the sea becomes a fleeting interest, something less than bone deep. Remember Enzo saying, "Time erases everything. When I was 17 I was so in love I could die for her, two years later I didn't even remember her name." This is something important that Luc Besson is trying to relate to us: some things are transient. They are opportunistic and convenient. Some things, however, will never go away. They are real and eternal.
The cinematography in this movie is quite astounding. Strange angles, deep coloration and dramatic scenery are Besson trademarks (think: The Fifth Element). Quirky characters and cramp inducing character comedy all lend this movie more than its fair share of charm. You laugh, you cry and you remember that while you ride The Tube or Subway to your cubicle job, there is a beautiful and trecherous world out there and some people are wise enough to live in this world.
Fact File: Jean-Marc Barr's character, Jacques Mayol is a Real Person, the holder of a dozen world free diving records and was the first man to descend to 100 meters (330 feet), a feat he accomplished in 1976. He followed this with yet another record breaking drop to 105 meters (346 feet) at the age of 56.
He is also the author of a book, Homo Delphinus, The Dolphin within Man:
"To hold the breath effectively, even though it seems paradoxical, it’s best not to think about holding it. You need to do it without thinking; you need to become the act of non-breathing itself." - Jacques Mayol