The official Poseidon site has put online the production notes for the film which include a section on the VFX work on the film. Director Wolfgang Petersen, Overall VFX Supervisor Boyd Shermis and ILM Supervisor Kim Libreri comment on some of the work in the 600+ shot project.
The VFX notes mainly focus on ILM's work including the opening shot of the film and the digital water and ship, and includes such details such as mentioning a 100 crew at ILM:
To get the notes select About The Film, then Production Notes and "Cutting Edge Technology and Effects Join Tried-and-True Filmmaking and Practical Sets" link at the top.
Thanks to PaulILMFan for the sharp eyes.