Funny, but building an island is not really that uncommon. For centuries countries have built their own man made islands. Basically they dump tons of materials into the water, preferably somewhere a little more shallow than normal and continue to fill it up until they end up with an island. Usually these areas are not as bothered by high and low tide problems and major waves and so on. They are usually built in more calm waters.

In Dubai they have built many of these islands. They look amazing from the air in the shape of the globe or a palm tree. These islands cost a small fortune to build though.