Luc Besson was initially unsure of whom to cast in the main role of Jacques Mayol. He initially offered the role to Christopher Lambert and Mickey Rourke and even considered himself for the role until someone suggested Jean-Marc Barr. Besson has a cameo appearance as one of the divers in the film. The Big Blue was the most financially successful French film of the 1980s gaining 9,193,873 admissions in France alone and played in French theaters for a year.
The original ending was intentionally left open for the audience’s interpretation, though considering the depth he's swam down to it suggests that he would be unlikely to make it back to the surface alive in normal circumstances. However, as the film suggests throughout, Jacques' body is not normal and following the incident upon waking in the hospital it can be construed that he feels he may now be more suited to an aquatic life and his death may not be a foregone conclusion.
Alternate Ending (US version)
In the US version the ending is extended with an additional scene. After swimming away with the dolphin, Jacques is brought back to the surface, only this time, in what seems to be an alternate reality.
Upon release, the movie was met with positive reviews in Europe. The movie was heavily edited for a US release and fitted with a new ending and soundtrack. The movie received negative reviews in the States.
With its extensive underwater scenes and languid score (as with nearly all of Luc Besson's films the soundtrack was composed by Eric Serra), the film has been both praised as beautiful and serene, and in equal measure criticized as being too drawn out, overly reflective and introspective. While popular in Europe, the film was a commercial failure in North America due to the studio's recutting of the movie to include a simplified "happy" ending. In the American version, Serra's score was also replaced with a soundtrack composed by Bill Conti. This version was only available on VHS and Laserdisc in the United States (both with 4x3 pan and scan transfers) and is currently out of print. The director later released a longer Director's Cut on DVD, featuring the original ending and an extended version of the Éric Serra score.
The film was dedicated to his daughter Juliette Besson who required surgery, having become ill whilst he was working on the film. Most film parts were shot in the island Amorgos of Greece.
Source : Wikipedia