Tom chases Jerry onto a dock, and as the chase climaxes, they soon end up in a can factory, turning into cans during the opening credits. After they come out in cans (one reads "Tom" and the other reads "Jerry"), Tom cuts the top with his nail and releases himself. When Jerry sees Tom, he jumps and runs outside of the can factory, with Tom chasing him, making the fish cans spill everywhere.
Jerry in his can rolls out of the way, and as Tom is carried out by the rolling fish cans and off the pier, Tom glides through the air and stops as his tail, then his arm, and then his body register that gravity is imminent. Tom dangles in midair, has his face stretched, and finally falls into the sea. Tom soon jumps out of the water, white with fear, followed by a huge, hungry shark. The cat grabs onto an offshoot of the pier and pulls himself down so as to flip himself just out of the way of the attacking shark below him. The cat is then splattered with a drop of water and jumps back onto the pier as the shark laughs evilly. Tom responds by throwing an anchor onto the receding shark's head, causing him to badmouth the cat as Tom taunts at him.
Tom returns to chasing the mouse when he hears his can clattering across the wood floor. Jerry stops at Tom's foot and leaps into the air, but is then caught and opened. The cat repeatedly shakes the open can to get the mouse out of it with no results, and sticks a finger inside to get bitten by the mouse, with painful results. As he finally pulls Jerry out of the can, both of them realize the situation; Jerry releases his death grip, shows his smile to the camera, and kicks Tom's face as he starts the chase. The two chase through the huts and across the pier until Jerry stops at the end of the pier while Tom goes off the end. The cat looks back to see Jerry waving at him and can barely turn back around before he slams into a porthole, taking on its shape, and then falling into the sea to meet the shark once again.
Tom swims out of the way and escapes the shark, who continues to snap at him. The cat climbs a ladder while the shark eats through the wood columns under the pier. The shark swims back and takes a leap toward the cat on top of the pier and is smacked on the head with an oar before falling back into the water. He emerges and glares at Tom as the cat taunts him once again... only this time the shark leaps out of the water and grabs Tom (and part of the pier decking) in his jaws. Jerry peers through the resulting hole at the terrifying situation below: Tom is hanging onto the oar, which braces the shark's mouth open. He breaks this brace, but fails when Tom uses his legs to brace instead, staving off doom for a little longer. Fortunately, Jerry saves him by dumping an entire canister of pepper into the shark's mouth, causing the leviathan to sneeze and launch himself around the water and into the can factory, turning into a big can with his frowning picture on it.
Jerry relaxes and gets a halo for his good deed, but is attacked by an ungrateful Tom, who grabs him and pops Jerry's halo with devil horns that appear on his head, chuckling evilly. Jerry chuckles innocently and sneezes himself out of the cat's hand, off his horns, and into the water, immediately followed by the cat. Tom scans the scene only to find another shark fin on a beeline toward him! Tom screams and panics and swims away at lightning speed, with the fin keeping pace. The fin, however, is actually Jerry's creation, who is now shown swimming underneath the water. Jerry turns his head toward the camera with an evil grin on his face, and as he continues to chase Tom, he then also grows his own devil horns while he continues swimming after the cat.