Krakken

The sky was salt and foam and darkness and muscle, shattering ship and bone and pushing them to the oceanfloor. Screams were cut short by unpredictable waves and sudden thunder. Jacob, with one massivve gasp of air, let go of the piece of wreckage he was holding and dove underwater to see what had attacked he and his shipmates.
Upon submerging, he immediately saw the beast in its entirety. The ocean was engulfed in tentacles wrapping around each other in a colossal tangle of snake-like limbs. To his left he could see one man being torn apart and another quickly pulled into the darkness below. Before he had time to react, a tentacle caught Jacob's legs and started dragging him down. He twisted and pushed, but the creature's grip was far too strong, each tiny sucker shredding the flesh from his body. Desperate, he pulled a dagger from his belt and shoved it into the heap of flesh wrapped tight around his legs. For a split second the ocean seemed to stand still. Then there was a loud, low groan and a pulsing wave travelled across the monster's body and burst from the Krakken's mouth as a shriek.
Wasting no time, Jacob propelled toward the wounded beast and plunged his blade into its skull. In one last movement, the Krakken grabbed Jacob and ripped him to pieces, whipped its tentacles around wildly, shrieked, then sank into the darkness. Above, the waters calmed and the circling birds flew down and ate.