… then why isn’t it pronounced “mah-RYNE”?
My guess is that it’s because ‘marine’ comes from Old French, while the other words came straight from Latin.
I guess it matters how much vocal resonance comes from your DI in bootcamp.
The OED says this about the -ine suffix (TL;DR: there’s no systematic reason for the pronunciation differences):
The termination is widely used in natural history and zoology in forming adjectives, with or without a Latin model, on the names of genera, as acarine, accipitrine, bovine, caprine, equine, feline, hystricine, murine, passerine, viverrine; in later use many are modelled on scientific Latin group names (based on the names of genera) with the plural ending ‑ina(neuter plural, originally with Latin animalia understood) or ‑inae (feminine plural, originally with Latin bestiae understood; later as a formal taxonomic ending for subfamily names, after the pattern of ‑idae used for family names), as gadine, lambeosaurine, mastodontine, milleporine, paradoxurine, pythonine. In these natural history adjectives the pronunciation is British English /ʌɪn/, U.S. English /aɪn/, usually unstressed; but in other words it is very various, depending upon the length of time the word has been in English, the channel through which it came, the place of the stress, and other circumstances: compare divine adj., supine adj. British English /ʌɪn/, U.S. English /aɪn/, marine adj. British English /iːn/, U.S. English /in/, feminine adj., genuine adj.1 British English /ɪn/, U.S. English /ən/, aquiline adj., bovine adj., leonine adj.1, alkaline adj. British English /ʌɪn/, U.S. English /aɪn/, and see the history of the individual words.
Pronunciation rules in English are basically: give it your best shot.
I’d drop the “best” from that.