Cavemen hunted massive animals to extinction in prehistoric days. You can accomplish a lot when you put a bunch of tiny humans with smart brains together, and a collective goal in mind.
All the humans would do is modify their ships to go kraken hunting, because humans like to attack what they fear and prove their mettle. So, they'd have kraken hunting ceremonies, possibly as a right-of-passage for manhood. But, the kraken will also have resources the humans can use...
- the meat can be sold
- the body parts (eg: the beak) sold as trophy to wealthy people
- the ink sold to writers / alchemists
- various body parts and fluids sold to alchemists, collectors, etc
The ships the humans made would evolve into something that would give a kraken a run for it's money, like massively over-engineered timbers and structure that could prevent a kraken from breaking the ship apart. Surround the outsides with spikes and things that hurt the kraken if it tries to wrap a tentacle around the ship. Dump massive loads of some kind of fluid into the water that the kraken doesn't like if the kraken gets the upper-hand. Cannons with chains would get fired that would act like saws flying through the air to shear the kraken's flesh and limbs.
Humans would find a way to fight and benefit from the kraken..possibly hunting them to extinction if the kraken didn't learn to avoid the ships.
Think of it this way...
In the Dishonored video game series, they reinvented whales into these nasty, sharp-toothed prehistoric buggers that would tear ships apart.
The ships evolved into metal-encased death machines that went out hunting the whales, b/c a) the whales were dangerous, b) the whales had valuable resources.
The same would happen on your world as the humans feel it's their imminent domain to conquer all.
The thing holding them back would be resources.
One reason the Native Americans in the United States lingered in progress compared to other people in other countries is because they lacked easily-accessible resources, like metals. While the Chinese were inventing gunpowder and fireworks, the Native Americans were still living in tee-pees and shooting bows-n-arrows.
So, the resources the people on-land had available to them, and the technology to harvest, process, refine, manufacture.. that would be the limiting factor.
If your humans are still running around with canoes and stone weapons.. yeah, stay out of the water.
But, if the humans advanced to metal-working, steel manufacturing, large timber working, etc... those krakens' days are numbered.
It depends on how readily available the resources are, and how well-equipped the humans can get to them... and then how smart they are in refining and using them.