Only a handful of people have traveled to such staggering depths. One of them is movie director James Cameron, who using a state-of-the-art vessel, dropped 35,000 feet, or about 7 miles, to the deepest place on Earth -- the Challenger Deep in the western Pacific Ocean.
DPI stands for dots per inch. Depending on the mouse make it will have certain presets (e.g 3000, 6000) and pressing it will cause your mouse to cycle through them. The higher the DPI , the farther the cursor on your screen will move when you move the mouse.
Some gaming mouse lets you config to any DPI within a range, for example, from 400 to 4000. Typically, they also let you set the buttons to increase/decrease DPI, or activate a specific DPI. Logitech G700s Mouse software, for setting the buttons to control DPI.