A woman and her partner, J., a professor of medicine, embark on a cruise to Singapore where J. is meeting with the International Infectious Disease Council. After the meeting, the pair plans to visit the Great Barrier Reef and then go skiing in New Zealand. The trip is a kind of trial honeymoon for the pair to see if they are a good fit living together.

The woman grows angry with the Australian passengers on board and decides that they hold no appreciation for the coral reef, like she and J. do. She compares the tacky souvenirs the Australians buy in gift shops the boat stops at to the ones that she buys, which she considers more refined. A recent divorcee, she imagines her ex-husband falling off the back of the ship and her leaving him to fend for himself in the open sea. 

When the boat stops on Happy Island, the passengers get out and are warned to avoid touching poisonous shells and coral. The woman thinks about how the boat’s crew must hate the passengers for their clumsiness and never-ending demands. When the other passengers begin to take a liking to J., she wonders if he is an Australian at heart and therefore if she shouldn’t marry him. 

The pair talks to the captain who reveals he someday hopes to discover a new island. After many passengers get sick and they pass through a rough storm, the weather clears up and they are able to visit the coral reef. When they arrive at the reef, J. and the woman split up so he can explore on his own. While J. goes off to explore, the woman looks out at the other passengers and realizes she has grown to know and like them all. 

On the last night of the cruise, all the passengers dress up for a costume party. At the party, a passenger she had previously felt sorry for announces that a comet he and his friend discovered has just been accepted by the international commission. Everyone celebrates, and the woman begins to reconsider the negative way she used to consider him, along with the other passengers. The woman is voted best costume by her fellow passengers and she simultaneously experiences happiness and shame for the ways she had underestimated the Australians for their kindness.