Day to consider the importance of the ocean to Japan as an island nation.
Marine Day (海の日, Umi no Hi), also known as "Ocean Day" or "Sea Day", is a Japanese national holiday usually celebrated on the third Monday in July. The purpose of the holiday is to give thanks to the ocean's bounty and to consider the importance of the ocean to Japan as an island nation.
Many people take advantage of the holiday and summer weather to take a beach trip. Other ocean-related festivities are observed as well. The date roughly coincides with the end of the rainy season () in much of the Japan mainland.
In 2020, the holiday will be observed on Thursday, July 23, a one-time move that was made as a special accommodation to support the opening of the Tokyo Olympics. Due to the postponement of the Olympics, the 2021 date will be moved to July 22, also on Thursday as a one-time holiday.
Source: Wikipedia: Marine Day