Greg Cox wrote:
As I recall, Chris Columbus was developing a Submariner movie a few years, but that seems to have sunk into the Development Abyss.
Universal Pictures had the film rights to Namor for a long time. Columbus was attached to direct at one point and then he left the project and Jonathan Mostow came aboard. From what Kevin Feige has said lately it sounds like Universal's option on the Namor film rights has expired and the rights have reverted to Marvel.