The influences of the hydrosphere on human life and activities around the world cannot be overstated. Seventy percent of the Earth's surface is covered by water. The human body is composed of mostly of water. All living creatures, especially humans, require water to survive. The hydrosphere has enormous influence on human activities because it is essential to human survival. Man's interaction with the Earth's environment and natural resources, including with the hydrosphere, has placed at risk those resources and, consequently, life on the planet. Sources of fresh water have been polluted through improper disposal of industrial waster and by inefficient, wasteful uses of sparse supplies, especially in arid regions like the Southwest United States and in Central Asia.
The oceans and seas, once assumed to contain plentiful supplies of food for human beings, are similarly endangered through commercial overfishing, by man-made pollution, and by the effects of global climate change, wherein water temperatures essential to support life forms are increasing and threatening the species that have historically existed there. In addition, as fresh water lakes and rivers are depleted by overuse or are diverted for man-made dams and irrigation systems, the fresh water that used to run into the saltwater oceans and seas has diminished, in the process increasing salinity levels in those oceans and seas.
This educator lives less than a half-mile from Lake Superior, one of the two largest freshwater lakes in the world (Lake Baikal in Russia being the other). Lake Superior, historically home to many species of fish upon which surrounding communities survived, is currently undergoing dangerous changes as its temperature rises and as invasive species of fish and plants -- species not native to the lake but introduced through careless human activities that destroy the existing ecosystems -- take over and deplete the native species.
The hydrosphere is vital to support human existence. It provides drinking water, water for agricultural purposes, and food and nutrients from fish and plants. Its interaction with the larger atmosphere, to say nothing of the moon, are all a part of life on Earth as we know it. Egyptian society, one of the most ancient on Earth, was formed around the annual patterns of the Nile River, patterns that began to change with construction of the Aswan Dam and which continues to change with inefficient use of the water supply by upstream countries like Sudan. As the Nile is manipulated by humans for our own use, the amount of fresh water flowing from it into the Mediterranean Sea decreases, causing the salinity levels (the ratio of salt to water) to rise to levels dangerous to native species in the sea -- species that surrounding countries have long relied on for food.
In short, the hydrosphere is seriously important to human life on Earth, and its influence on human activities, despite its importance in supporting human life, is regularly adversely affected by the influence of human activities on the hydrosphere.