The Ricardos and Mertzes are in Miami Beach, Florida. Ricky and Fred are complaining because they don't seem to be catching any fish on their excursion. They're also not happy at all the time their wives are spending shopping, not to mention how much money. Ricky suggests they should ask the girls along fishing so they stop shopping. Fred disagrees at first until Ricky reminds him of how much Ethel must be spending. The boys leave and the girls get to the room. They're both loaded down with packages and discussing how much they've spend on clothes. Lucy has spent $68, that's 8 weeks clothing allowance for her. Ethel's spent $72, as far as number of weeks clothing allowance, she declares she should live so long! They hide their packages and plan to demand the boys take them fishing. The boys will undoubtedly refuse so the girls will just say they'll just go shopping, then spring the expensive clothes on them.
The boys return and Lucy executes her plan and tells the boys they want to go fishing. She's speachless when they readily agree. Ethel tries to talk the boys out of it, but they insist. Lucy introduces a challenge, the boys versus the girls to see who can catch the bigger fish. The wager will be $140 plus tax (the cost of the clothes), but Lucy rounds it to $150 before Ricky started asking too much about how she'd arrived at her original wager.
Since Ricky has said his boat is a "yinx" (jinx), Lucy insists they get their own boat. Ricky and Fred take the bet and are happy that the girls will not be pestering them on their own boat.
Lucy and Ethel are alone and Lucy decides they should buy the biggest fish they can get their hands on and hide it on their boat to assure victory. They run to the pier and return with a giant tuna complaining that there was no room in the hotel refrigerator to store it until morning. The hotel's cooler was full from 2,000 ice cream molds in the shape of shriner's hats. Instead they put the fish in the tub and call down and order 4,000 ice cubes to keep it chilled. They leave to explain to the hotel what the ice cubes are for.
The girls leave and the boys enter with their own 100 tuna. They suggest hiding it in the tub, but Ricky remembers that Lucy always bathes the baby when he comes in from playing so they take it over to the Mertzes bathtub.
The girls return and Ethel decides to to her room to bathe. Ricky returns and insists on bathing but Lucy tells him they have the whole Atlantic ocean at their feet, why bathe? He pushes so she tells him she'll prepare the tub while he looks for swim trunks for Little Ricky. Lucy runs to the bathtub to get the fish and on her way out the door decides to hide it in the closet. Fred enters, dragging his fish, he had to move it because Ethel is wanting to take a bath. Lucy slips out of the room and brings the fish over to the Mertzes to put in their tub. Lucy goes back to her room and insists on bathing even though Ricky told her that the hot water tap is busted. He tells her to bathe at the Mertzes. She goes over and insists she's going to bathe in her own tub. She calls up Ricky pretending to be the hotel operator requesting that he and Fred are wanted by the manager.
The boys leave and Lucy runs in to take a shower and discovers the tuna in the tub. She's perplexed, didn't she just take the tuna to Ethel's tub? Ethel thinks Lucy's finally lost her mind until she goes in and sees the fish for herself. They try to retrace their steps and figure out how the fish got back there.
The boys return to the Mertzes room confused about the request from the manager. Ricky goes in to see Lucy in the tub, as she was supposed to be bathing at the Mertzes but finds a fish. He and Fred try to figure out how it got here as they thought they left if at the Ricardos.
Simultaneously they decide to just get rid of their fish, the boys will put it in the trash, the girls are going to dump theirs down the elevator shoot.
The doors to both rooms open and the girls run into the boys both sets carrying their giant fish. They all accuse each other of tryin to cheat on the bet and decide they will all go out on the same boat so there won't be any funny business. Just then a hotel attendant arrives with Lucy's 4,000 ice cubes.
The next day on the boat everyone has their fishing poles in the water, including Little Ricky, who the men claim is part of their team, in case he catches the biggest fish.
Ricky then gets a nibble and reels in his catch. I tiny fish no larger than a minnow is on the end of the hook. The girls chide him. Lucy suddenly gets a bite on her line, it feels like a biggie! She starts reeling it in when Ricky's rod goes over the side of the boat. Ricky then goes over the side to get his fishing pole.
Lucy fights with her fish and slowly reels it in. Ricky pops out of the water holding on to his fishing pole which is snagged on Lucy's line.
Ricky is fished out of the water bawling Lucy out. He insists they return to land. Lucy complains because of the bet but that little minnow that the girls were making fun of, just won the boys each $75.
Ricky starts jumping around wildly and drags a fish out of his shirt, it got stuck in there when they were in the water. Lucy proclaims victory as the fish was attached to Ricky and she'd just caught Ricky!