During the race at the dog track, Dave uses his powers to make the last place dog win, but there is red in the quarter poles at the race track which should make his powers go away and the dog to fall back.
Early on, it's established Dave can't swim, in general (seeing red having nothing to do with anything), since he grew up in the mountains. However, he is able to swim to the bottom of the ocean and rescue Dunlop near the end.
Sylvias buys an ice cream cone at the race track which is rather tall, when he sees the thugs a few seconds later the camera from a different angle shows the ice cream cone is considerable smaller.
When Dave and Sgt. Dunlap are on the balloon coming out of the sea, they are under water, but a few seconds after rising out of the sea. Dave and Sgt. Dunlap are talking on the balloon and their clothes are completely dry.
In the undersea sequence some fish are superimposed. However these are fancy goldfish, a domesticated fish that will not survive for long in salt water.
Dave Speed is ludicrously framed, arrested for murder, and sent for execution four times on pure hearsay; there's no investigation or attempt to recover Dunlop's body, nor any evidence of a crime, other than Rosy Labouche's say-so.
Despite the balloon being made from a bubble gum inflated by Dave, the seams are clearly seen.
In the scene where Willy and Dave are rising from the sunken boat to the surface on the bubblegum balloon you can see droplets falling off Willy's chin, proving he is not really under water.
When Dave Speed swims to the bottom of the ocean to rescue Sgt. Willy Dunlop (trapped in a boat's built in freezer) the ocean floor is perfectly flat and has no sea life or plants. Revealing that it's obviously a sound-stage water tank.Sgt. Willy emerges frozen stiff but the boat's power would have given out after being sunk.
When Dave is climbing around the plane to look at Evelyn through the window, the red stripe on the plane has no effect on his super powers.
The movie depicts several botched execution attempts against Dave, his survival owing to super powers. After the first botched attempt, under American law Dave's lawyer should have demanded a reduction in sentence since repeated shocks of electricity constitute cruel and unusual punishment. (Italy doesn't have the death penalty.)
In the first submarine shot after Dave Speed has escaped from prison by diving into the sea scratches of the pool window (or camera) are visible.
When Willie shows up at Dave Speed's apartment, Dave Speed is levitating on the ceiling reading a Superman comic. Impossible since Dave loses his powers when he sees red. Superman has a red cape and even the logo on the front of the comic is outlined in red.