The Portland, Maine sludge-metal quartet Ocean is the latest in a long line of arty metal bands who have slowed their riffs down, and down, and down, until the swells match the pace of restful breathing, and the pauses between each wash of distorted guitar noise feel like your heart stopping. This group’s debut album is an assured and creepy exploration of this kind of death-crawl blues, with long guitar chords towering over the crisp, equally spacious percussion, with fierce growled vocals occasionally coming in to add that distinctive death metal touch, half-silly and half-frightening.

Of the three long tracks here, the second, “Salt,” is the best example of the group’s powerful sound. The album, the liner notes say, has been “mastered to be played at a higher volume,” and it’s certainly true that as the volume rises the band’s utter mastery of its chosen sonic attack becomes ever more apparent. The song moves at a suitably glacial pace, taking 12 excruciating minutes to build to a stunning climax. Along the way, the guitars grind away at slow-moving riffs, hints of melody creep in only to fade away, and the drums gamely keep time with the barely moving crawl. Soon, the vocal is grunting unintelligibly amid the swirling riffage, and the song unexpectedly explodes into a tornado of darkly melodic minor-key guitar with crashing, tinny drums under the white-noise storm. It’s a grim, fearsome, and icy assault, and if it were only about 20 times faster, it’d be worthy of Scandanavian black metal gods like Darkthrone.

But Ocean seems to be aiming for something much different with its music, achieving as much chilly darkness with relentlessly slow and even playing as faster metal bands do with sheer technical prowess. In contrast, the final track “The Fall” opens with a barrage of rapid drumming that seems to suggest Ocean changing tactics, but things soon slow down into a dread-inducing stagger, with grunted vocals spat out over a backdrop of droning keyboards and churning molasses-core riffs.

There’s certainly no shortage of bands doing the slow metal thing these days, with pioneers like Sunn O))) and Boris still going strong and their influence creeping up into a whole new generation of experimental-minded metalheads. Ocean is clearly part of this new generation, and its debut is perfectly crafted and immensely satisfying. The band has its tight, sludgy sound down cold, and further distinguishes itself with the occasional graceful incorporation of melody and beauty into an otherwise doom-laden assault.