What are the qualifications of an island?

Question

-How big does it have to be?

-Does it have to be visible even during high tide?

-Does it have to be made with soil or sand? What if it's made of ice, rocks, shells, or corals?

Answer 1

um... it has to have water on all sides. this is the definition, so this is the qualification. nothing else matters.

make it a good day.

Answer 2

An island (IPA: /ˈaɪlənd/) or isle (/ˈaɪl/) is any piece of land that is completely surrounded by water in two dimensions, above high tide, and isolated from other significant landmasses. Very small islands such as emergent land features on atolls are called islets.

It can be made of soil or rocks.  

If you put a lump of soil and surround it with water, technically, it is an island - completely useless islet, but an islet nevertheless

Am

Answer 3

Surrounded on all sides by water, comes from the floor of the body of water (not floating), smaller than a continent.  Those are pretty much all the requirements.  They can be made out of anything.  There are other subcategories of islands with more specific characteristics.