The open ocean of any depth, where animals swim or float freely is called a pelagic zone. Salinity variations in the open ocean normally ranges from 33 to 38 percent.
20,000 to 30,000 thousand miles
Depth is a measure of distance between the surface and the ocean floor.
To find out the ocean`s depth
'Sonar". And determines depth. The ocean floor topography can be mapped by 'sonar scanning'.
They are sometimes used to measure the depth of an ocean
Scientists know the depth of the ocean by using technology like the Deep Worker or the "Alvin". It takes them to the bottom of the ocean so they can study ocean life. Also ships use sonar (SOund NAvigation and Ranging) to see what the depth of the ocean is.
The average depth of the Indian ocean is I dont know honestly