Board Thread:Naruto Discussions/@comment-26636534-20160527151459/@comment-3568954-20160601084118

Ocean:a very large expanse of sea, in particular, each of the main areas into which the sea is divided geographically.

sea on the otherhand is defined as :the expanse of salt water that covers most of the earth's surface and surrounds its landmasses.(often in place names) a roughly definable area of this.(often in place names) a large lake

so you see when kabuto says Shintai_deep sea he doesn't mean like say the pacific ocean

Amegakure is seemingly surrounded by the lake that jiraiya's body is resting in. its a massive lake so large that its called a sea.

its no different than any landlocked body of water that is called a sea for example the Black sea

the lake that surrounds Amegakure could be as deep as an ocean, there are real lakes that are really deep such as lake Baikal in Russia which has a depth of 5,387 feet thats 1.020265 miles deep