As a side note from all of the Sneasel / Gligar / unbanned mons / things hype, Water-types are pretty great in Gen 6, too. None of the newly released Pokemon resist powerful Water-type STAB, and few common old Pokemon do either as Dragon-types are still as uncommon as ever and Grass-types are rarer because of Sneasel / Gligar's ability to nail them hard. Plus, Water-types resist a lot of popular new attack types, mainly Sneasel's Ice-type attacks, as well as new Steel-type attacks to hit Fairies, and many have enough natural bulk to sponge neutral attacks common in the tier.
In terms of specific Pokemon; Chinchou, Mantyke, Tirtouga, and Frillish all come into mind. Chinchou still has great speed, bulk, and resistances, and also gets Volt Switch and Thunderbolt. Mantyke is a scary sweeper, having the bulk to tank most attacks and the ability to set up Rain, with Swift Swim and powerful Rain boosted Hydro Pumps to power through opponents. Tirtouga is part of the Sturdy + Shell Smash + Berry Juice sweeper group, and is great because it doesn't give a shit about common sneasel + meditite priority checking. Frillish is an oddball but still has a very viable niche; it walls Meditite to hell and can burn everything with Scald. All it really has to fear is the Stealth Rock-weak Sneasel, and it can just switch out at that.
In terms of moves Water-types still retain the advantage they had last Gen. Hydro Pump was nerfed but it's still pretty powerful; coming off the the solid SpA stats of most Water-types lets it be used to smack opponents real hard, even when unboosted. Surf is solid Water-type STAB as well, though not as powerful as Hydro Pump it still usually gets the job done with perfect accuracy. Scald is also still as annoying, if not even more annoying, than it was last generation. Burns hurt a lot more this generation since there are so many new prevalent physical attackers, and even the special attackers hate the added damage.
All in all, Water-types are terrific and definitely should not be forgotten when building teams.
EDIT: Also forgot about Skrelp, which people claim are great but I haven't really used myself. Adaptability + Scald / Surf / Hydro Pump is bound to hit every hard, and it also has an added niche of walling the fuck out of Meditite as well as beating unboosted Swirlix 1 v 1 with Sludge Bomb.
EDIT 2 @ below: Other than Zen Headbutt. I don't know how often exactly ZHB is used on Meditite but I've only seen it like once so idk :/