pacific
Don't assume that "deepest lake"and "most voluminous lake" are the same thing. Search for "deepest lake" and "largest lake by volume". It turns out that the answer depends on whether you consider the Caspian Sea to be a "lake" or not (it's salty, though not as salty as the ocean, and is geologically speaking actually more of a "fossil ocean"). If you consider it a lake, then it's the most voluminous, but Baikal is the deepest. If you don't, then Baikal is both.
The most species are probably in the ocean.
Mantle
The Pacific holds half of the worlds ocean water.
The Pacific Ocean
Lake Baikal
Lake Kartha
There is the Pacific Ocean, the Atlantic Ocean, Indian Ocean, and the Arctic Ocean.
In the sea, but there is a significant volume on land, as liquid or ice.
Pacific Ocean.
It's the Arctic Ocean.
it is the pacific ocean