He was probably a Samaritan, or possibly a Jew. He came to Athens at a time when, with the exception of Proclus, there was a great dearth of eminent men in the Neoplatonist school. It was for this reason rather than for any striking ability of his own that he succeeded to the headship of the school on the death of Proclus in 485. During this period, the professors of the old Greek religion suffered persecution at the hands of the Christians and Marinus was compelled to seek refuge at Epidaurus. The year of his death is not known.
His chief work was a biography of Proclus, the chief source of information on Proclus' life. The publication of the biography is fixed by internal evidence to the year of Proclus's death; for he mentions an eclipse which will happen when the first year after that event is completed. It was first published with the works of Marcus Aurelius in 1559; it was republished separately by Fabricius at Hamburg in 1700, and re-edited in 1814 by Boissonade with emendations and notes. He is also the author of a commentary (or introduction) on the Data of Euclid, and a commentary on Theon's Little Commentary. There is also a surviving astronomical text which discusses the Milky Way.