Computational science is very different from computer science. Though a computational scientist can be expected to know the basics of how hardware and software operates, their specific tasks revolve around using their advanced computer knowledge to solve scientific and engineering problems by processing large amounts of data.
This means they often find themselves on interdisciplinary teams. A computational scientist may work in astronomy, medicine, social sciences, public policy analysis, or virtually any branch of engineering.
Programming, including specific techniques for scientific and high-performance applications, takes up a large part of the coursework. This is rounded out with statistics, advanced and applied mathematics, and computer modeling.
This means that successful students tend to be skilled at logical and systemic thinking. General scientific knowledge will often come in handy, as will experience in any computing field.