The episode opens up with the closing of the Krusty Krab. SpongeBob leaves to go and take out the trash. When he goes around to the back of the Krusty Krab. He reads some of the dumpster writing and one of the dumpster writings reads: "Krabs is a ****." When SpongeBob reads the word (which happens to be an expletive), a garbage man angrily asks him if he kissed his mother with that mouth, then SpongeBob answers, unaware that it was not a serious question, that he does it sometimes, but not recently. He asks Patrick what it is and he says that the word is a "sentence enhancer."
The next day, SpongeBob walks into the Krusty Krab and says the swear to Patrick in a greeting manner and then use it over the intercom. The Krusty Krab customers are appalled by the profanities said by SpongeBob and then leave. Squidward tells Mr. Krabs the story. He decides to tell them that the swear is bad word number 11 of a list of thirteen profanities, though Squidward says that there isn't more than 7. SpongeBob and Patrick decide to wipe the said expletive from their tongues and promise Mr. Krabs that they will never use it again.
Later, they play their favorite game, Eels and Escalators. Patrick gets escalators, but SpongeBob always gets eels and eventually he loses the game. After that, he utters number 11. Patrick then races to the Krusty Krab to tell Mr. Krabs with SpongeBob trying to stop him. During the chase, Patrick says the swear word so SpongeBob starts racing faster than Patrick to tell on him. Patrick hitches a ride above an Ice-Cream Truck, but doesn't reach the Krusty Krab. SpongeBob bursts through the front door and tells Mr. Krabs that Patrick said the swear, but in a complicated way. Patrick then joins along, but they always end up changing the subject to something else.
Eventually, Mr. Krabs stops their gibberish and they say what they need to tell him. When both of them say the bad word, Mr. Krabs is offended. He takes SpongeBob and Patrick outside and returns with cans of paint.
Mr. Krabs is about to give SpongeBob and Patrick the job of painting the Krusty Krab, but he hits his foot on a rock, throws the paint away and says all thirteen expletives while complaining about hurting his foot on the rock. When SpongeBob and Patrick hear all the swears, they run to Mama Krabs' house to tell on him. When they all reach her house, they repeat the same swears during their complicated explanation. This makes her faint, but shortly after Mr. Krabs scolds SpongeBob and Patrick for saying all those bad words in front of her.
Then she regains consciousness, and states that all three of them should be ashamed for saying all those words in front of her, and that if they are going to talk like sailors, then they are going to work like them. She then gives all three of them the task of painting her house with a fresh coat of paint as punishment for saying those words to her. She then hits her foot on a rock, too, and even though Mr. Krabs thinks that his own mother said a swear, it is actually the horn of Old Man Jenkins' car. The episode ends with all the characters laughing.
This episode became controversial as this episode teaches children the inappropriate words, even though the episodes bleeps them out with marine sound effects (i.e. foghorn, seal barking, dolphin chirping, etc.) so the kids don’t know what they said. The point is to deter swearing.
This episode also drew criticism from the Parents' Television Council and the fans who felt it encouraged children to use profanity. Despite this, the episode taught that it was wrong to do so and that it results in punishments: when Mr. Krabs told Patrick and SpongeBob they were using bad words, they were horrified. And, when they used them again, they were punished with painting the Krusty Krab and Mrs. Krabs' house.
"Sailor Mouth" was ranked #96 during the Best Day Ever event on November 9–10, 2006.
If one would look closely on the dumpster, one can see the words "Patchy was here." This is a reference to Patchy the Pirate.
Originally, when he lost Eels and Escalators, SpongeBob was going to say: "Go (dolphin chirp) yourself!" and Patrick was to say: "(dolphin chirp) you, too!" However, this was removed as it would have been inappropriate for younger audiences.
According to two interviews found here and here, the idea for this episode came from a childhood experience:
Learning a curse word is a classic thing that all kids go through. It was inspired by creative director Derek Drymon's experience of getting in trouble as child for using the f-word in front of his mother. Drymon said, "The scene where Patrick is running to Mr. Krabs to tattle, with SpongeBob chasing him, is pretty much how it happened in real life." The end of the episode, where Mr. Krabs uses more profanity than SpongeBob and Patrick, was inspired "by the fact that my Drymon's mother has a sailor mouth herself."
In the SpongeBob SquarePants Movie game, bad word number 11 is said twice in Planktopolis.
This episode was quoted to be Chris Pine's favorite episode.
It could have been Plankton who wrote the phrase on the dumpster, due to his disliking of Mr. Krabs. It could also have been a customer as Mr. Krabs is known for being a terrible businessman.
This episode is based on the reputation of sailors to use an abundance of profanities. The episode's title is based on the term "sailor mouth," meaning someone who swears a lot. Other terms include "swearing like a sailor." Among other names are foul-mouth and potty mouth (no relation to Potty the Parrot).
In the Russian dub, the amount of bad words Squidward knows is 8 instead of 7.
In the Brazilian dubbing, Betsy Krabs has a deep masculine voice.
Dolphin noises are heard in other episodes, but they are not used to censor expletives. An example would be the dolphin noises in "Jellyfish Jam." Another one would be SpongeBob making dolphin noises in "The Paper" and "You Don't Know Sponge."
Some of the dumpster writings:
Up with bubbles, down with air
Patchy was here
Dogfish ♥s Catfish
Starfish rool (reference to Patrick)
Nematoads are people, too
Squidward smells GOOD (the last word added by SpongeBob, who assumed that the writing was unfinished).
Krabs is a (dolphin chirp)
The "Squidward Smells" writing behind the green mess on the dumpster looks very simiar to the "Something Smells" title card both in appearance and name.
Patrick calling Mr. Krabs a "red sweaty guy" may be a reference to the season one episode "Arrgh!"
In the alternate network versions, the dolphin noises are replaced with trombone talks used in some Peanuts specials. As an example: "Krabs is a (trombone talk)."
When Squidward whispered in Mr. Krabs about what word SpongeBob said, he actually said "chubbybandorism."
Some of the profanity sounds may be a reference to part of a Rocko's Modern Life episode, where Rocko and Heifer are at an appliance convention to help Rocko to find the correct tools to clean up Rocko's kitchen. They come across a book that has some of the profanity sounds heard in this episode.
The plot of this episode is similar to the plot of the Powerpuff Girls episode "Curses," where Blossom, Bubbles, and Buttercup learn a curse word, and start constantly using it. Also there were random cartoon sounds covering up the words, just like this episode.
When Mr. Krabs asks, "What kind of things?," the captions say: "What things?"
When SpongeBob and Patrick are racing to the Krusty Krab it is established that SpongeBob can run faster than Patrick, except when in "Life of Crime" they are racing to the police station, the two are evenly matched.
When SpongeBob says: "Yea varily. Now, let's play a nice wholesome game of "Eels and Escalators." It shows the game board, but SpongeBob's left arm and the dice that SpongeBob had on his left hand are, indeed missing, while Patrick is sitting down. The next scene when Patrick says: "Oh boy, my favorite!" He is lying down, again. This may be due to the still paint scene error.
When Mr. Krabs says: "From top to bottom." Before his right foot hits the rock, he had his teeth together because his mouth wasn't in sync with the dialogue.
When Mr. Krabs' right foot got hit, he held his left foot which was uninjured. Mama Krabs had the same error.
When Mr. Krabs pulls the penny out of Mama Krabs' pocket, it is silver instead of bronze.
In the scene with the kids laughing at SpongeBob saying bad words, A child's hat is red. In the next scene, The child has a blue hat.