Marinus of Neapolis was probably a Samaritan, but just possibly a Jew. He became a convert to the Greek way of life and joined the Academy in Athens where he was a pupil of Proclus who was head of the Academy. In fact when Proclus wrote a commentary on the Myth of Er, he dedicated it to Marinus.
Marinus succeeded Proclus as head of the Academy at Athens in 485. We are told in  that:-
... he lectured on Pappus' commentary to Book V of the Almagest (in particular his discussion of parallax); and there are still extant lecture notes on the Data of Euclid.
... wrote a commentary, or rather introduction to the Data of Euclid. It is mainly taken up with a discussion of the question - what is meant by given?
In fact Marinus was a great believer in mathematics, something which he shared with fellow late Neoplatonists. He said (see for example ):-
I wish everything were mathematics.
Although Marinus followed closely the views of his teacher, Proclus he did show originality which is much to his credit. The level of his regard for Proclus is evident in the biography that he wrote Life of Proclus in which he :-
... praised and eulogised [Proclus].
Yet when Marinus felt that Proclus was in error he was quite prepared to give his own views. For example Proclus had claimed that Plato's Parmenides was concerned with gods. Marinus, quite correctly, pointed out that Plato's work in rather concerned with 'forms'
The article  by Tihon is an interesting account of two previously unknown commentaries on astronomical topics by Marinus. One concerns the Milky Way and Marinus discusses whether it is affected by precession. As early as the 5th century BC Democritus had correctly understood the Milky Way to be due to a multitude of faint stars. However this was still not the accepted view in the time of Marinus, who argues against this hypothesis in this commentary. Marinus did claim, however, that the Milky Way was part of the sphere of fixed stars and so underwent precession in the same way as the fixed stars.
In the second commentary by Marinus described in , he corrects the rules for the direction of parallax in longitude given by Theon of Alexandria in his small commentary on Ptolemy's Handy Tables. Marinus makes use of ideas by Pappus in making his corrections.
Article by: J J O'Connor and E F Robertson