The family decides that summer to invest in an outboard engine for the Sea Cow, which opens up opportunities to explore much more of the coast. Gerry is entranced when they discover an archipelago of small islands that are home to a number of strange and wonderful sea creatures. Though the family agrees to several trips out, these eventually stop as the family becomes bored. Eventually, Gerry decides to use his upcoming birthday to his advantage by asking for a boat and a bunch of other scientific equipment.
Gerry's desire to be able to travel by himself shows that he is growing up; this desire for independence is part of becoming mature. Therefore, asking for a boat situates the boat itself as what will, per Gerry's understanding, allow him to become appropriately mature and achieve a more adult sense of independence.
Gerry creates a list for each family member that caters to their interests—Margo's list consists of fabric and pins, while Gerry asks Larry for books. Gerry waits for the right moment to ask Leslie for a boat. After helping him with a ballistic experiment, Gerry manages to back Leslie into a corner, question his boat-building abilities, and extract a promise to build him a boat. While Leslie builds and curses on the back veranda, Gerry happily sets to work digging ponds to house his new creatures and lining them with pink cement.
The care that Gerry takes in constructing his ponds shows that he's beginning to develop an interest not just in having animals, but in keeping them in enclosures that are sturdy and mimic their natural habitats. In this way, Gerry works to engage with animals on their own terms and not try to domesticate them in the conventional sense but rather, he wants to make domestication mimic the wild.
The day before Gerry's birthday, everyone goes into town to buy presents, take Lugaretzia to the dentist, and stock the cupboards. Though they all agreed they didn't want a crowd at Gerry's birthday party, they ended up inviting 46 people due to a lack of communication. After her dentist's appointment Lugaretzia is in no state to help with party preparations, so Spiro steps in to help.
The fact that the way the Durrells communicate with each other fits into the general sense of absurdity on the island again suggests that Corfu is a place where such things are simply bound to happen, if only because people tend to accept the absurdity as normal.
The day of the party, Gerry inspects all his gifts and then Leslie leads him outside to show him the boat. It's the most beautiful thing Gerry has ever seen, even though it's almost circular and has a flat bottom. As a final touch Leslie pulls out the mast, which needs to be fitted after it's launched. Gerry suggests launching immediately, but Leslie insists that the boat needs a name first. Gerry decides to call it Bootle just when Larry suggests Bumtrinket. Thus, much to Mother's dismay, the boat becomes the Bootle-Bumtrinket.
Gerry's description of the boat as a whole suggests that it's not actually a particularly fantastic boat; rather, it seems beautiful because of the feelings of independence that Gerry has attached to it. Though that sense of independence is a mark of growing maturity, the name Gerry gives the boat isn't: it's silly, nonsensical, and makes it clear that Gerry is a child.
Margo, Peter, Larry, and Leslie carry the Bootle-Bumtrinket to the jetty, where Gerry and Mother open a bottle of wine in celebration. Finally, the boat bearers toss the boat into the water. Peter gets in to fit the mast as Larry points out the issues that might arise by fitting a 20-foot mast into a craft so small, but Leslie doesn't listen. As Peter fits the mast, the boat promptly overturns and dumps Peter into the water. Larry and Leslie begin yelling at each other about who's the cleverest until finally, Peter emerges. Leslie, extremely angry with Larry, changes to a swimsuit and takes his yacht manual down to the boat. The mast ends up being three feet tall.
When Larry and Leslie turn to arguing with each other rather than thinking about Peter's safety, it reinforces both how cocky and self-important Larry is, as well as how self conscious Leslie is about his boat building. Though Leslie insists he is indeed educated, the particulars of the boat suggest that he might not be as adept at understanding the concepts presented in the yacht manual as he'd like everyone to think.
Spiro arrives with help and takes over the kitchen not long after, drinking and singing loudly as he cooks. Theodore is the first guest to arrive. He gives Gerry a book on freshwater biology. Gerry finds that most other gifts are useless, though he's thrilled to receive a pair of puppies. He locks them in the drawing room with Roger, but this proves a poor choice: when the family opens the doors to allow guests in, they discover the puppies made quite the mess. Larry suggests the puppies be named Widdle and Puke and though Mother protests, the names stick.
As with the Bootle-Bumtrinket, Mother's concern over what people might think of the names Widdle and Puke shows that she wants to fully embody the image of upstanding English people. Deciding on such silly names is proof that all of her children have more or less adapted to the relaxed and unconcerned way of life on Corfu, as they think little about what others might think.
The party rages on and several guests, including Leslie and Spiro, begin a traditional Greek dance in the living room. Dr. Androuchelli arrives late after delivering his wife's baby. Spiro gives the doctor a hard time for having six children, which he deems ridiculous. The party goes until dawn, and Gerry thinks it was an exceptional birthday.
When Spiro teases Dr. Androuchelli, it shows that even the locals aren't always fully behind the culture of the island. However, it's also worth remembering that Spiro spent eight years in America, which may have colored how he views life on Corfu.
The next morning, Gerry takes Roger, Widdle, and Puke out on the Bootle-Bumtrinket's maiden voyage. The sea seems bluer and more beautiful than usual. Gerry observes the clams, the feathery sea creatures, and the pouting fish that live in the reefs. He even finds a baby octopus. Finally, when the sun begins to set, Gerry heads home, the bottom of the boat filled with tubes and jars of sea creatures. Roger, a "marine enthusiast," studies the jars intently.
When Gerry attributes Roger's interest in the jars and tubes as being indicative of his enthusiasm for marine biology, it shows that Gerry is also willing to anthropomorphize Roger in such a way as to make it seem like they have more in common. By doing so, Gerry can feel even closer to Roger.