It has a post-rock atmosphere with prog-rock elements but a metal sound. Apparently this is post-metal or prog-metal, which I’m not too familiar with as a genre, probably should be. But then again I guess Tool could fall in this category, too, I’ve just never thought of them this way. And thinking about it this way I ralize the difference between post-metal and prog-metal. Tool is more on the prock-metal side essentially coming from a prog-rock/art-rock angle just adding more metal weight to instrumentation. While The Ocean is more heavy on the post-rock vibe with epic instrumental spaces where massive and rhythm-heavy riffs bridge calm and sorrow melodic sections.
In any case, this is a fantastic record, takes me on a journey, and I definitely want to follow it up with its successor Phanerozoic II right away.