GOTM is an ambitious name for a one-dimensional water column model for marine and limnological applications. It is coupled to a choice of traditional as well as state-of-the-art parameterisations for vertical turbulent mixing. The package consists of the FORTRAN90 software, a number of idealised and realistic test cases, and a scientific documentation, all published under the GNU public license. GOTM is, of course, not complete (and will never be). Whoever is missing any feature in GOTM, is warmly invited to contribute to GOTM and add her or his personal preferences or needs.