The water is murky.
Sometimes directors must make decisions based on what appears to be more appealing, sacrificing some credibility in the process. When we were watching Titanic, it never occurred to us that the water didn’t appear to be as clear as it should have been. The water would be significantly darker, murkier, and teeming with sea life in actuality. That would have been far more true to life, but it would have been a nightmare to film, let alone cinematography-wise.
