It's just after midnight, and the weather is awful. The wind and rain are howling at 30–35 knots. Ocean Voyager is doing 10 knots in a rough sea, like a runaway train careening down a mountain in a storm at night. It's impossible to sleep in more than spurts, and I regret I can't reach through my midriff and hold my stomach steady. For some subconscious reason, it's instinctively important for me not to give its contents back to nature. Getting your sealegs in rough weather isn't a pleasant experience.

After four broken, tossing hours of unconsciousness, my eyes snap open in the darkness. At 4:30 a.m. I head up to the bridge to find out if this madness will have an end. The second mate tells me that we will arrive on the Yamato site at 7:15 AM, earlier than expected due to a positive current from the wind. This puts our arrival almost three hours away. It's good news, but offset by howling winds that threaten our chances of diving today.

At 6 a.m., I return to my cabin and give sleep another desperate try — knowing that all on board who aren't working this shift must be presentable at 9:00 a.m. for the blessing of the sea, a Japanese tradition that will precede any activity at the Yamato's site. When I finally doze off, I dream of a dark tunnel of clouds two hundred miles long above Hiroshima, stretching down all the way from the port city of Kure, over Kagoshima and beyond into the open ocean of the East China Sea to Okinawa. At the south end of this dark tunnel, a beautiful, large, peaceful white ship basked in the serene glow of brilliant sunshine. This dream ship, like Ocean Voyager, was steaming south.

At 8:15 a.m., P.H. wakes me with a sharp shout, telling me to get ready so I won't be late for the blessing. At 9:00 a.m., we at last reach Yamato's site. I suddenly sense the awful human loss that occurred here on this patch of open ocean, 54 years ago. Being at the site of a maritime disaster as huge as the Titanic or Yamato is emotionally disorienting, and the reality of the human and historic tragedy that occurred here closes in on all of us as we gather on the deck.

For Masami Hashimoto, 73, this is a place of memory. He was 18 years old when he set off with 3,331 other sailors aboard Yamato, on April 6, 1945. His duty was on the radar range finder, high up on the ship's bridge tower.

This morning, he is ready early for the blessing of the sea — as is Sokichi Shibagaki, 78. Sokichi was 24 when he came off duty from Yamato at the Kure Naval Base, just before the battleship left for the Okinawa Defense Mission. His younger brother replaced him on Yamato and never returned.

Sakutaro Nishihata, 78, was a young engineer on the Yamato design team that quietly built the biggest battleship ever put to sea. He joins Hashimoto and Shibagaki on Ocean Voyager's helipad, high above the rolling surface of the sea.

The three men steady each other as the rest of us gather for the blessing ceremony. They carry large bottles of sake and bouquets of flowers to the rail over the sea, then pause for quiet, personal reflection.

In Japan, sake is more than a strong drink; it is used for spiritual ritual and for cleaning and purifying wounds. It was also a very human part of Yamato's last night at sea. In his book, Requiem for Battleship Yamato, junior naval officer Yoshida Mitsuru recalls the night of April 6, 1945, before the ship's suicidal mission:

"1730 hours: over the ship's P.A. – "'Distribute sake to all divisions'...We exchange glasses of sake in ceremonial farewell. . . . What awaited us was death and nothing else. Death beyond a doubt. No matter how splendid its raiment," he wrote, "death is death."

Flowers, too, are very much a part of Yamato's story. The great battleship carried the emperor's golden symbol on her bow, a 5-foot chrysanthemum made of gold-leafed cedarwood, and its last mission was code-named Operation Kikusui, " Floating Chrysanthemum."

Now, Hashimoto, Shibagaki and Nishihata slowly pour the sake into the sea, then toss bouquets of flowers on its rolling surface. The rest of us gather at the railing and do the same. The ceremony to bless the sea is intimate, just quiet prayer and reflection—a greeting to the spirits of those lost on that great ship below.

Now Masami Hashimoto steps back from the railing, his sake and flowers gone. He is 73 but trim and gifted, with a warm face and character. He tells us how much he appreciates being here with his shipmates' spirits today. He is smiling, but there are tears in his eyes.

Sokichi Shibagaki steps forward to say that he, too, is glad to be with the spirit of his younger brother today — the brother who, he believes, died in his place. He remembers how his mother had made a sweet cake for his brother to take with him to sea. There was no food then to speak of, and sweets were almost a memory, but his mother had managed the impossible for her son who was going off to war.

Sakutaro Nisihata, however, is in a different mood. As he withdraws from his reflections, he is angry, and he lectures all of us:

"Listen to me, war is wrong — all war is wrong —it is a lesson we must learn."

Together, the three men then go quietly below decks.

By 2:00 p.m., the weather has improved, and P.H. tells me that today we'll be able to launch Ocean Voyager's two submersibles, named Jules and Jim. Thirty minutes later, P.H. begins his dive to the Yamato's wreck aboard Jules, and I start my descent on Jim.

It's 11:00 p.m. by time P.H. and I finally return from our first dive of the mission. It's been a very long day, and I'll report on the details of our dive after a good night's sleep.