>>32816602It is not a broken type by any means, but it has all the tools it needs to fit any role imaginable, being maybe only under steel and fairy in terms of viability.
There are so many water type pokemon that you're sure to find at least one of them to cover every possible niche in the game. We have water sweepers, water boosters, water clerics, water wishpass, water regen, water spinners, water hazards, water stall, water pivot, water weather, water terrain, and many many more. Hell, now we even have a water "shuckle" called pyukumuku.
Water types not only have some key resistances and only two weaknesses, but they also tend to have well-rounded stats and guaranteed access to ice moves, which provide a reliable answer against grass mons. Grass mons are in such a natural disadvantage that some water types have more to worry about from a giga drain volcarona or an energy ball lele than from a fucking tangrowth.
Water pairs incredibly well with practically any other type; I can't think of a single dual type with water on it that has it as bad as rock/steel or ice/grass (maybe rock/water? but all the mons with this typing are either swift swim sweepers, shell smash sweepers, or both). Rain is also an amazing weather condition to rely on, having arguably the best weather setter (pelipper) on its side, too.
Then there's scald. Almost all water types worth using learn it one way or another, and scald-spam has little real drawbacks: fire types cannot be burned but they get hit hard, and mons that resist it might not appreciate getting burned. Mons with water absorb/storm drain (most of which are water types) are good against scald users. Out of the things that resist water (water itself, grass, dragon), two are hit hard by ice beam so there's really no point on using anything other than water to fight water, if you don't have an electric option I mean.