Marine Day (Umi no Hi)

What Is Marine Day?

Marine Day is a national holiday dedicated to expressing gratitude for the blessings of the sea and celebrating the prosperity of Japan as a maritime nation. It originated as "Sea Memorial Day," observed on July 15th, before becoming an official national holiday in 1996. Under the "Happy Monday" system, it now falls on the third Monday of July — in 2026, that's July 20th. July 15th remains an important date for understanding the historical roots of this holiday.

An Origin Story Beginning With an Imperial Voyage

The establishment of Marine Day is rooted in historical events tied to Japan's modernization and its relationship with the sea.

• The return of the Meiji Maru: In 1876, Emperor Meiji embarked on a tour of the Tohoku region aboard the lighthouse inspection ship Meiji Maru, returning safely to Yokohama Port on July 20th. To commemorate this event, then-Communications Minister Shozo Murata designated July 20th as "Sea Memorial Day" in 1941 — the origin of today's holiday.
• Becoming a national holiday: Following extensive public advocacy for greater awareness of Japan's identity as a maritime nation, a 1995 revision to the Public Holiday Law made it an official national holiday starting in 1996 — reportedly the world's first national holiday dedicated to the sea.

The Science of the Sea and Wellbeing

The refreshing feeling of spending time by the ocean has real physiological and psychological grounding.

• The "blue space" effect: Spending time in coastal environments — taking in the sound of waves and the expanse of water through sight and sound — has been shown to regulate the autonomic nervous system and lower levels of the stress hormone cortisol.
• The psychoacoustics of "1/f fluctuation": The sound of waves washing in and out contains a pattern known as "1/f fluctuation," a balance of regularity and unpredictability. This sound pattern has been shown to increase alpha brain waves, promoting deep relaxation and improved concentration.
• Sea spray and negative ions: The fine water droplets created when ocean waves break are rich in negative ions, which are thought to help activate the respiratory system and lift one's mood.

Interesting Facts About the Sea

• The Meiji Maru as a cultural treasure: The Meiji Maru, the ship connected to Marine Day's origins, is preserved at Tokyo University of Marine Science and Technology and is the only iron-hulled ship in Japan designated as an Important Cultural Property.
• The ocean's "conveyor belt": The ocean hosts a massive circulation system called "deep thermohaline circulation," which carries water — and heat — around the entire globe over roughly 1,000 years, helping to keep the Earth's climate stable.
• Seawater and the chemistry of life: The mineral composition of seawater is remarkably similar to that of amniotic fluid and blood plasma in the human body — one piece of evidence supporting the idea that life originated in the ocean.
• Why the sea looks blue: The ocean appears blue because red light from the sun is absorbed by water while blue light scatters and reaches our eyes — a phenomenon explained by Rayleigh scattering and the selective absorption of light by water molecules.
• The potential of marine resources: Japan's exclusive economic zone (EEZ) is the sixth largest in the world. It holds significant promise as a source of seabed resources like methane hydrate, as well as renewable energy from wave and tidal power.

Tips for Enjoying Marine Day

• Take a walk along the coast or visit somewhere with an ocean view, taking advantage of the "blue space" effect to help clear your mind after a busy season.
• Incorporate ocean-derived minerals into your meals — try cooking with natural sea salt, or enjoy seaweed and seafood as a way to balance your body's mineral intake.
• Take a moment to learn about the issue of ocean plastic pollution — understanding the current state of marine debris is a meaningful step toward more sustainable habits.
• Visit a historic ship like the Meiji Maru or a maritime museum, and learn about the technology and history that shaped Japan's modernization.

Let the Endless Blue of the Horizon Wash Away Your Doubts

The period from July 15th to 20th is a time to reflect once again on the blessings we receive from the sea, our common origin. The same waves that carried Emperor Meiji safely home long ago are, in essence, the same waves before us today — part of one vast energy circulating the globe. Has the busyness of recent months narrowed your view? Today, look out toward the distant horizon and take a broader view of your own life. Just as the sea welcomes every river, every experience you've had ultimately flows toward something richer. Let the sea breeze carry you forward into a bright and promising summer.