July 17 is a national holiday -- Umi no Hi, or Day of the Sea. Ostensibly, it commemorates a famous day when the Emperor Meiji returned from an extended sojourn in northern Japan to the Port of Yokohama, and is meant to instill appreciation for the sea's bounty. However, it was established as a national holiday in the 1990s when consumption was on the decline, so most people recognize it for what it is: an excuse to go out and spend money. Appropriately or not, the TV schedule for Umi no Hi is filled with nature documentaries.

At 4 p.m., NTV will present a 90-minute special called "Seimei no Umi: Chi-kyu Judan (Sea of Life: Around the Earth)." Boxer Hidekazu Akai and actress Noriko Kato travel to various places around the globe to study the effects of global warming. In Alaska, they visit an Inuit community whose livelihood has been adversely affected by a steady drop in the volume of ice on the sea. The result has been a decrease in the population of animals that the community depends upon for food. The rising sea has also caused devastating erosion of the seacoast, swallowing up homes and facilities.

They also go to Madagascar, whose climate and ecology have been affected by the warming of deep sea currents that come all the way from the Arctic. At 7:30 p.m., NHK-G will air part 2 of a special natural history feature called "Dinosaurs vs. Mammals" (Part 1 airs July 16 at 9 p.m.). Using computer animation, the program attempts to explain that long window of time, about 200 million years ago, when dinosaurs and mammals occupied the earth at the same time. Mammals were much the underdog, the food of larger dinosaur predators like the Tyrannosaurus. The program tries to explain theories of why mammals survived and dinosaurs disappeared. The program also shows how homo sapiens' evolution was a direct result of this ancient competition, and ponders some mysteries of the prehistoric record. Did the babies of Tyrannosauruses have feathers? Were there mammals big enough to fell and devour a large dinosaur?