ELI5 Coal to Diamonds - can pressure really turn coal into diamonds?

Superman did it in Superman 3. If coal turns to diamonds through pressure, could we dump a bunch of coal on the ocean floor to turn them into diamonds faster?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: rnbwmstr, bizitmap, stuthulhu, nevm, iamplasma & sir_beard   To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected] ... we love hearing from you!