July 20th: 海の日 (Marine Day)

Umi no hi, or Marine Day, became a national holiday in Japan in 1996. Before 1996, it was originally known as Marine Memorial Day, which was established in 1941 to commemorate the Meiji Emperor’s return to Yokohama from his journey to the Tohoku region in 1876. This holiday was also established to express gratitude for the gifts of the ocean, and to recognize the importance of the ocean as a maritime nation. Since it is relatively a new holiday, there are no traditional ways of celebrating Umi no hi, but Japanese people take advantage of this day through participating in aquariums events, water competitions, and taking a trip to the beach.  

Reference: Office Holidays