In a made up fight Oscar knocks Lenny through a billboard adverting Jaws then it's intact again.
When the Shorties tag "Sharkslayer" on the wall, the painting of Oscar wearing armor and carrying a sword disappears after it is first seen.
Many of the bigger shark species, like the great whites and great hammerheads seen in the film, are typically solitary creatures. Smaller and medium-sized species like gray reef sharks and scalloped hammerheads are far more social. Granted, great whites don't live in groups, but recent studies have shown they have a far more complex social structure than previously thought and enjoy the company of others of their kind every once in a while.
When (the) Seal shows up at the start of the film, he falls straight down onto the pavement and makes an audible slapping noise, not muffled by the water in the slightest.
There are suggestions in the movie that the sunken ship used by the sharks as a hideout is supposed to be the Titanic. The would be impossible, because the movie takes place along a tropical reef such as the one off Key West Florida. This is over 1000 miles away from the Titanic. Also, the sunken Titanic is 10,000 feet deep. The sharks and other fish in the movie can not swim that deep.
Lenny tells Frankie that he's cold because he's cold blooded. In fact, great white sharks are one of four types of shark that are warm blooded.
When Lenny says "Okay." while untying Dewey from the fishhook, his mouth doesn't move.