Not going to make the obvious CotT joke. Instead, here's a bad pun!
Krakens are Gargantuan, aquatic magical beasts (have fun exploring dungeons) with 20 HD. Even post-mouthpick, they've got eight natural attacks (though six of them are pretty weak). Unsurprisingly, they're great grapplers, with each limb getting Improved Grab, Constrict and 30 to 60 feet reach. Everything that is to be said about teleportation and FoM at these levels has been said before.
As with all D&D octopodiformes, they've got the ability to create clouds of ink (useful if your entire party has blindsight), and jet at high speeds. Note that neither ability requires being underwater.
There's also a handful of SLAs, each usable once per day, with not even half the kraken's HD as CL. Don't expect anything impressive from them.
Compared to similarly-leveled characters, both monsters and PCs, a kraken will simply fall short. -0 LA.