Whenever the body is seen underwater, an Olympic-sized swimming pool is seen with completely clear water and lane markings instead of the murky water in the tiny pool that is seen in front of the mansion.
As a man is being drowned, his blue lenses in the entire scene are not visible and the true color of his iris is visible. This is a major mistake as the movie focuses on the color of his eyes all the time.
As a man comes out of the murky-looking pool, his pants are colored blue because of the blue color that was used to make the water look murky.
To make the pool look murky, a blue color was added to the water. This is clearly visible as the water splashes and in the lengthy scene where its gushing out of pipes.