Posses are arguably the best heavy infantry in the game, with them gaining further buffs from the Witch Doctors and .Bull Snappers
Be warned though, you will be limited in your choices and you'll find cracking heavy armour can be a pain without Rask. and fury management is simply not there (without a few inventive chices, which I'll get to later). Cryx will give you a hard time as well as Gators get a lot of bonuses from living models. Plus Calaban is not exactly regarded as a great choice as far as casters go, limiting your choices further.
However, your support pieces are amazing. Witch Doctors are pretty much compulsory, and you can turn the tables on Cryx by using dominate undead on the Wraith Engine, just for the looks.
Wrong Eye and Snapjaw are amazing.
WE's Voodoo Doll is just hilarious when cast on a Gargantuan. Remove its spirit so it can't be forced. You may also want to consider putting a Bull Snapper in his battlegroup if you've also taken Rauluk Moorclaw, as putting spiny growth on his marshalled jack (rather fun on a Rover) makes it a bit difficult to crack.
Feralgeists are your fury management due to being incorporeal. If you've got a beast that's run hot and you can't get the fury off of them. Stick a Feralgeist in front of them before the following turn when they make the frenzy check. The beast will just thrash uselessly at the Feralgeist due to a complete lack of magical attacks. Ferals are also good for contesting objectives too (they can't hold as they're incorporeal). Certain factions will probably have to commit their caster to get rid of the Feral.
Wrastlers are pretty much your staple warbeast with the "fastball special" being one of Blindwater's favourite tricks. They have pretty ok attacks, with the bite being the strongest one, but it's still a bit average. Rask makes them ridiculously strong with Fury cast on them.
Ironback Spitters are the only shooting attack in the entire faction (well, Croaks too). They're a bit pillowfisted and their animi is considered to be useless by some. But they do have their uses, namely girded and their spiny back plates. The latter just slays infantry. The Ironback can walk into a unit then if it walks away, every time the enemy free strikes it they take
d6 damage.
There's a lot more to go through, but here's a small taste of what Blindwater play like.