Yukio Mishima’s The Sound of Waves tells the story of Shinji Kubo, a poor but passionate young fisherman who lives on the remote island of Uta-jima in the Japanese archipelago. Shinji lives with his widowed mother and his younger brother, Hiroshi. He works hard each day aboard the Taihei-maru (a fishing boat belonging to the seasoned fisherman Jukichi Oyama) in order to provide for his family in the wake of his father’s death. When Shinji spots a beautiful woman he’s never seen before on the island, he becomes entranced by the young pearl-diver, whose name is Hatsue—but when he learns that she is the daughter of Terukichi Miyata, one of the wealthiest men on the island, Shinji fears he has no chance at winning her love. One night, after a meeting of the island’s Young Men’s Association led by the brash, cruel, promiscuous, and wealthy Yasuo Kawamoto, Shinji stops at Yashiro Shrine to pray for the health and happiness of his family—and for Hatsue to notice him.
One day, while gathering wood for his mother near an abandoned watchtower, Shinji runs into Hatsue, who has gotten lost on her way to the lighthouse. He shows her the way and begins to feel that she cares for him, too—yet when he hears a rumor that she is engaged to Yasuo, he becomes sad. After Shinji drops his pay envelope on the beach while helping some sailors pull in their boat, Hatsue finds it and returns it to Shinji’s home, then goes to meet him on the beach where he has gone to look for it. There, Hatsue tells Shinji that the rumor about her and Yasuo is nothing but a lie. They share a kiss and make a plan to rendezvous again soon—but when they meet the following night at the home of the lighthouse-keeper and his wife, to whom Shinji brings fish each evening, the lighthouse-keeper’s wife’s mention of her daughter Chiyoko’s crush on Shinji offends Hatsue. Shinji assures Hatsue that the rumors about him and Chiyoko, too, are just that—rumors. However, Chiyoko does pine for Shinji, unbeknownst to him.
A heavy storm strikes the island, making fishing impossible. Shinji and Hatsue meet at the abandoned watchtower, but Shinji arrives early and falls asleep near a fire. When he awakens, he finds Hatsue drying herself near the flames—she is naked. Hatsue is startled when Shinji wakes up and demands he look away, but he refuses to do so. Hatsue tells Shinji that in order for her not to feel embarrassed, he must undress, too. He does so immediately. The two kiss and embrace, but Hatsue does not want to make love—she thinks doing so before marriage is wrong. Nevertheless, they declare their love for one another, then head home together down the mountain.
Unbeknownst to them, the jealous Chiyoko spies them from the lighthouse. She quickly tells Yasuo what she’s seen, and Yasuo begins spreading the rumor quickly throughout the village. While Shinji and his mother struggle to understand why their neighbors have begun to look at them strangely, Yasuo makes plans for revenge against Hatsue. He waits for her to come down to the village well to gather water late at night, then tries to assault and rape her. His attempt is thwarted by an angry swarm of hornets—yet he forces Hatsue to let him walk her home.
When Terukichi Miyata learns of the rumor about his daughter and Shinji, he becomes enraged and forbids Hatsue to leave the house. Hatsue begins writing letters to Shinji and leaving them in the water-jar at the front door. Shinji’s fellow fisherman Ryuji brings him the letters each day and delivers the notes Shinji writes back to her. Meanwhile, Chiyoko prepares to return to Tokyo where she attends university. As she bids farewell to Shinji, he pays her a nice compliment. She feels guilty for the wildfire of gossip she has started and decides to try to find a way to make up for her wickedness.
Shinji’s mother, fed up with the gossip, decides to confront Terukichi Miyata herself—but when she arrives at the house and asks to see him, Hatsue sheepishly relays that her father will not see Shinji’s mother. Hatsue and Shinji make a plan to meet in secret, but on the night of the meeting, Terukichi is waiting in the shadows for Hatsue. He drags her back to the house as Shinji looks on.
Pearl-diving season begins, and when a peddler brings some fine wares to the beach for the pearl-diving women to peruse, he offers to give away a fancy purse to the winner of a diving contest. Hatsue wins the contest and the bag, but she gives it to Shinji’s mother as an apology for her father’s rudeness.
One afternoon, Shinji receives a visit from the captain of one of Terukichi’s freighters, the Utajima-maru. The captain offers Shinji a job. Shinji is skeptical and insists he needs to get Jukichi’s permission, but the captain says he’s already visited Jukichi and secured it. Shinji takes the job. On the day of departure, he learns that Yasuo, too, will be joining the crew of the freighter. At the docks, Hatsue gives Shinji’s mother a package for Shinji—it contains a charm for good luck, a letter, and a picture of herself. As the freighter makes its way from port to port toward Okinawa, Shinji works hard at his post while Yasuo spends all his time bragging to the other seamen about how one day, he will marry Hatsue and own the freighter himself.
By the time the ship arrives in Okinawa, a dangerous typhoon is brewing. The freighter ties itself to a nearby bonito ship and the two boats make their way into harbor, tying themselves to a buoy. That night, while keeping watch through the storm, Shinji and Yasuo see one of the lines tethering the ships to the buoy snap. The captain says someone needs to volunteer to tie a lifeline to the buoy. Yasuo says nothing, but Shinji offers himself up. He dives into the sea fearlessly and works hard to swim out to the buoy, fasten the line, and return to the ship. In the morning, the storm clears.
Shinji’s homecoming to Uta-jima is celebrated across the island—word of his heroic deed has made it home. Chiyoko, who refuses to come home for summer vacation, writes to her mother and confesses that it was she who started the rumor about Shinji and Hatsue, and that she will not return home until Shinji and Hatsue are engaged or wed. The lighthouse-keeper’s wife gathers several village women—including Shinji’s mother—and heads for Terukichi Miyata’s house to confront him with the truth about the rumor. Terukichi says he has already chosen Shinji to be his daughter’s husband—Shinji proved his worth on the freighter, passing the test Terukichi himself lined up for both Shinji and Yasuo.
Shinji and Hatsue celebrate their engagement by praying at Yashiro Shrine and bringing fish to the lighthouse-keeper and his wife. The lighthouse-keeper offers Shinji and Hatsue a tour of the lighthouse, then leaves them alone at the top of the tower to watch as the beacon’s bright beams shine light into the dark ocean. Shinji and Hatsue vow to protect each other forever.