How do they build an oil rig
In that latter case, you get underwater oil and offshore oil rigs. In the “middle” of the ocean, the seafloor is primarily basaltic crust generated by volcanic activity at the mid-ocean ridge. There are a number of different types of 'oil rigs' in the ocean. In relatively shallow water (less than 200 feet, or so) we can use 'jack up rigs'. These are triangular shaped floating vessels with long legs on the three corners. When the rig is I am interpeting this question as " how do they build an oil rig" as a literal interpretation. and not as how do they drill for oil and not how do you decide where to drill and not how do you produce oil from a hole in the ground.