The continents are thicker and less dense than the materials that make up the ocean basins.
The Hydrosphere
A large area between continents underwater is called a ocean basin or a mid-ocean ridge. Ocean basins are vast regions of the seafloor that separate different continents, while mid-ocean ridges are underwater mountain ranges that can extend for thousands of kilometers between continents.
They do touch the ocean floor. they're like a giant mound, and the beaches flow into the water.
Your question makes no sense, an ocean basin is an OCEAN not land area and therefore including it is impossible.
No, in general the Atlantic basin is very young and the ocean is still getting wider each year. This means that the continents either side are moving in the same direction as the ocean floor so oceanic crust is not yet being forced down into the mantle at the basin margins.
The Pacific Plate is the largest tectonic plate, covering parts of the Pacific Ocean basin as well as parts of the continents of North America and Asia.
The Arctic Ocean Basin
the continental shelf ;)
Abyssal Plain.
The true edges of continents are known as continental margins, which consist of the continental shelf, continental slope, and continental rise. These margins mark the transition from the continent to the ocean basin and can extend hundreds of kilometers from the shoreline.
When two continents split, a divergent boundary is formed. This boundary creates a gap between the separating continents, which can eventually become an ocean basin as new crust forms and fills the space created by the separation.
The continents that do not have Pacific Ocean coasts are Europe and Africa.