Much later, when Sirius Black remembered his past life, the very last memory of this existence was how surprised his cousin Bellatrix had looked, just immediately after firing from her wand the stunner that knocked him into the Veil hidden deep within the bowels of the Ministry of Magic. It was almost as if that insane Death Eater had actually expected her wizard relative to perform some sort of clever dodging or blocking against the spell that would keep him from falling through the mysterious arch from which no-one had ever survived passing through the slightly fluttering curtains covering this curved structure.
Well, he hadn't. Putting up a successful magical defense against that stunner from dear Bella, anyway. As for the other thing…
Without the passing of even a fraction of a second right after seeing Bella disbelievingly watching him topple backwards, a blast of numerous other sensations then burst into Sirius' mind. He was lying on his side upon something hard that was totally soaked, while also twisting and lifting and rolling, all at the same time. A wave of salty water from the puddle he was sprawled in splashed into the wizard's open mouth, leaving him spluttering. This choking sound immediately became an agonized shriek, as his stomach exploded with pain.
Clutching at his middle, Sirius curled up in a fetal position, blinking away both his sudden tears and the patter of heavy rain also falling onto his face, as he dazedly stared upwards into the evil grin of somebody looming above, whom he'd never seen before in his entire life. That stranger in his hooded robe, standing over the prone wizard while easily keeping his balance, continued to aim his wand directly at his prisoner, while beginning to roar with laughter at the gleeful shout made by someone behind Sirius, "Gi' 'im another one, Sam! 'E needs a proper innerduction to Azkaban, don't yeh think?"
In the bow, Bernie Tooley finished off his cruel suggestion with a malevolent guffaw, while his mate enthusiastically pulled back his right boot in a prompt response to that proposal. From the looks of things, that cully laid out in the bottom of the Azkaban Prison ferry was going to lose a couple of teeth to Sam's savage kick in the next second or so. Not that anybody who mattered would care the slightest about this. Those wand-users sentenced to the harshest terms in the British wizarding world's most dreaded prison deserved whatever they got, and mere physical pain wasn't the worse that would eventually happen to them. Not when the Dementors came calling, sooner or later.
The very presence of those soul-sucking monsters drifting around Azkaban in their ghastly patrols had decades earlier resulted in serving at that prison being considered the most detested task possible by the entire Auror corps. No sane wizard wanted to be closer than necessary to those horrific creatures, so there was a distinct lack of volunteers whenever a guard position at that penitentiary opened up. As a consequence, the Ministry of Magic quickly became accustomed to assigning to Azkaban those who either couldn't or wouldn't get out of this disliked duty using any means whatsoever: the incompetents, failures, drunks, malcontents, bullies, and other genuinely unwanted members of the Auror Office.
Every one of those recently-appointed and very sullen wizarding warders before long transferred all their resentment and ill-tempers at having to work at bloody Azkaban towards the prisoners they were guarding, who couldn't die fast enough on their own to suit their keepers. And if that happened a little sooner than expected, during some sort of…encouragement to behave or else, well, as long as you didn't do this right in front of the whole Wizengamot, you stood a damned good chance of getting away with it.
All of the above flashed through Bernie's mind, as he casually glanced over Sam Hartman's bulky shoulder towards the stern of the boat. There, a blank-faced Frank Higgins was incuriously watching someone about to learn the proper rules of absolute obedience to any Azkaban staff member, all while continuing his usual job of steering their ferry with his wand through the pitching seas, strong winds, and blinding rain of today's half-gale. Satisfied that the boatman wouldn't cause any trouble as long as their latest prisoner got delivered to the prison dock in somewhat reasonable condition, which meant breathing on his own, but not actually capable of crawling off their arrived boat already a third of the way there, Bernie switched his gaze back to where Sam was about to happily rearrange somebody's face.
When the pointed toe of the worn boot came hurtling right at his head, Sirius Black finally had enough. There was no wand at hand, so that wizard instinctively used his only other means of defense. In a blurring transformation into his Animagus form, a human dressed in a thin prison robe shifted into a hundred pounds of furious canine, easily ducking under the foot about to crash into a black-furred animal skull. Lunging up off his stomach onto his paws, the enraged Grim opened his massive jaws as the dog instantly struck for the closest target certain to completely incapacitate his opponent.
His right leg helplessly swinging skywards after somehow missing its kick, Sam just as instinctively flinched away from that beast who'd managed to appear from out of thin air. The man desperately twisted his torso away from the dog going right for the man's groin. Sam was fast enough to put his left leg into a blocking position protecting that extremely valued part of his body, but it really didn't matter. The Grim himself shifted in his leap accompanied by a turn of his fanged muzzle, towards the now totally exposed inner right thigh, with its extremely vulnerable femoral artery.
The agonized scream that next occurred nearly burst the eardrums of the other two horrified men, as very sharp animal teeth sank full to their gumline into human flesh, with the snarling dog chewing deeper into the seized limb, using every bit of power in the canine's strong jaw muscles. Unthinkingly dropping his wand as he collapsed into the bottom of the boat, Sam started to pummel with both his fists against the top of the dog's head clamped onto his leg. The Grim only ignored this, as Sirius gave one last vicious bite and felt a gusher of hot, coppery-tasting liquid then spurt into his mouth.
As an aghast Bernie now heard Sam's screams turn into a wailing moan, the other prison guard continued to shakily point his wand downwards at the intermingled, writhing bodies before him. The Auror at the boat's bow was too terrified to get closer to the savage battle in the middle of the small vessel, and he couldn't fire off any spells capable of killing or harming that damn dog without hitting Sam! However, in the very next moment, the black beast let go of his defeated adversary, and it spun around to stand on all four feet, its lips savagely drawn back to show every jagged tooth dripping with blood, as it crouched lower, clearly about to leap directly at Bernie.
Right in the middle of the casting of this exploding curse, Sirius had jumped with all the power in his canine legs. Not forward at his foe, like an unintelligent animal that didn't know about wands, but as a thinking being who realized there was no chance of reaching the man ahead without being hit by whatever spell that was coming. Instead, the Grim hurled himself sideways, right over the side of the boat, to splash into the angry ocean. Coming up for air, the dog desperately paddled away from the boat, hoping he could get far away enough in the next couple of minutes to lose himself among the high waves and heavy rain created by the storm around them.
Unable to stop from finishing the spell, much less move his wand to track and hit the escaping dog, Bernie's eyes widened with horror, as he saw exactly where his hex was going. Flashing over an unconscious, pale-faced Sam, the Reducto scored a direct hit on the right lower leg of Frank at the stern, who'd done nothing but stand stock-still and gape at the unexpected carnage of the last few seconds. Which further continued, as the boatman was promptly blasted off the small craft, leaving behind the gobbets of flesh that were the only things left of his severed leg. Also out cold even before he hit the water, Frank soon sank out of sight into the waves, his life ending without the ferryman knowing this at all. At least, until another operator of an intangible, mythical boat soon picked up Frank to take this glum human onto a last journey, as a favor for a fellow professional.
Not that Bernie noticed this, or even how the boat, which was no longer under anyone's control, had fallen off its course to start wallowing in the rough seas. Staggering forward to helplessly stare at his mate, who barely seemed to be breathing, Bernie pointed his wand at the massive leg wound still pumping out far too much blood, and he tried and failed to remember his Auror training in healing spells. This latest example of his ineptitude that had gotten him transferred to Azkaban in the first place did manage to keep the prison guard busy enough that he paid no attention to whatever was taking place behind him.
Sirius, on the other hand, was staring in disbelief at the gigantic wave at least three stories high and swiftly coming right at him. Taking the deepest breath possible, the dog ducked under the surface and swam forward with all his strength. A second later, everything turned dark around the Grim and icepicks stabbed into the animal's ears as the wave passed by overhead. Frantically struggling towards the dim light overhead, Sirius eventually came up again, gasping for air as he floated for a few seconds. A sudden thought then struck the man in the canine body, as he twisted around to peer through the storm.
When the wave hit the ferry broadside, the enormous wall of water instantly flipped the whole craft over, while at the same time throwing Bernie completely out of the boat, to then bury the stunned guard in the sea under the onrushing wave. Giving in completely to panic, Bernie clawed for the surface, only to swim into something that was both firm and soft. Clutching at this unknown object, the guard's flailing hands rubbed over a…face.
Instantly realizing he'd just grabbed hold of Sam's sinking body, Bernie started to scream, losing a big gulp of air until he managed to shut his mouth while once again trying to ascend. Beginning to pass out, Bernie still kicked and scrabbled as hard as he could, until he popped to the surface. Only to see the side of the overturned boat just a few inches away from his face, and at that same moment the vessel was shoved hard forward by another wave, which if it wasn't the size of the previous one, it was still strong enough to propel the whole ferry in an abrupt collision with Bernie's head. Letting out a last hopeless gurgle, the dazed guard slipped under the water and never came back up, leaving only a single person still alive of the four men that had been in the Azkaban ferry only a minute or so ago.
Floating among the waves while rising and falling in the water, Sirius warily eyed for a few moments the keel of the upside-down boat about a hundred feet away. The thick fur of the large dog was keeping bearable the chill of the ocean, so the Grim waited with predator patience for any of his former warders to climb onto that drifting platform. Eventually realizing he was likely the only survivor, Sirius held up his canine nose, and he sniffed deeply while paddling around in a circle. Yessss…there was the smell of growing plants in that direction. Staying motionless in the water until another big wave lifted him high, Sirius anxiously stared ahead, to have his heart leap in his chest at seeing a black line on the horizon. Giving a whuffling sigh of relief, the Grim started a steady swimming stroke towards his chosen destination.
A couple of hours later, it was still raining hard. This meant there was nobody around the small, deserted North Sea beach to observe how a large animal tiredly scrambled out onto the shore from the low surf created by this protected section of the coast. Taking a few steps further onwards over the shingle beach, the dog then gave itself a thorough shake, spraying water far and wide from its fur, just like any other Canus lupus familiaris. However, the self-possessed glance now done by this beast around its present surroundings was clearly intelligent. Satisfied that there were no witnesses in the vicinity, the Grim loped ahead along the beach, soon disappearing inland through the growing dark.