Revealing mistake: In the fight against the first 2 prison guards, in the shots furthest away from action Ice Cube is replaced by a leaner stuntman. (00:10:40)
Revealing mistake: When Ice Cube is escaping from prison and the prison sniper tries to shoot him down, the actor might as well been doing "pew-pew" noises with his mouth, because his finger is not even on the trigger. (00:13:00)
Revealing mistake: Right after Darius blows the boats, Steele is on the dock firing at him. It is shown that he shoots a couple rounds but his finger is not on the trigger. (00:24:00)
Revealing mistake: The wider shot (after the POV) of the boat going up the ramp to rescue Agent Toby Lee Shavers from the Virginia police is a miniature work recognizable at first glance. (00:24:55)
Revealing mistake: When Darius stomps on the police car with the speedboat, an explosion starts from the bottom of the car just the moment the boat nicks the roof. (00:25:00)
Revealing mistake: Ice Cube peels the sticker from the hard drive, but he starts peeling it from the right side in the first shot, the left side in the close-up - in fact looking at the numbers you can tell it' s a mirrored shot. (00:32:00)
Revealing mistake: On the receiving end of a prison sex joke, 'Sergeant' Cobb shouts irate to his men to kill Stone. An RPG is fired at him but Stone apparently makes a tank as maneuverable as a bike and just dodges it. The rocket hits a truck, but if you look at the trajectory, the CGI rocket gets inside the truck making it explode from the inside without breaking the side of the truck itself, which is pure witchcraft. (00:54:45)
Revealing mistake: Aboard his M2 Bradley Stone dodges the other tank's cannon shot, which destroys the helicopter without piercing its outer frame; the helicopter simply implodes. (00:55:10)
Revealing mistake: When XXX and his friends open the cheese truck, look into it and let Toby work his magic, you can see in the distance above the black SUV the cars blocking the road to allow filming. (01:08:30)
Revealing mistake: As the bullet train is chased by the helicopters in formation, the helicopters fly as obvious CGI constructs. (01:23:35)
Revealing mistake: When Cobbs slams Darius against the door after dodging the knife he pulled out, Ice Cube is replaced by a stuntman. (01:26:40)
Revealing mistake: As Lo bids farewell to Darius, you can get a good look at the back of his neck when he catches the keys with his not-so-injured-anymore hand. When he drives away the camera zooms on an XXX tattoo that simply wasn't there. (01:34:25)
Revealing mistake: Obvious stunt double when Darius is escaping from jail.
Answer: To break the surface of the water making an easier penetration. Hitting water at high speeds can be like hitting concrete. By stirring up the water it "softens" the impact.
EMTurbo