Oil Platform

How do they move around without sinking to the bottom of the ocean?

These platforms are as wide as entire football fields and stand at least 10 to 20 stories tall.

Most offshore drilling vessels/platforms are designed to be moved from location to location. The majority of exploratory wells drilled are failures, so it would not make sense to build a permanent structure at the start of a drilling campaign. We use a variety of styles of temporary/mobile structures to drill exploratory wells (and often to drill the development wells, too). These are called Mobile Offshore Drilling Units (MODUs).