These are the numerous birds that are associated with the water. Some members are fairly obvious: ducks, geese, swans, loons, cormorants, gulls, and terns. While others aren’t quite as obvious: herons, coots, rails, cranes, storks, kingfishers, and moorhens.
While there are raptors that feed on fish (osprey, bald eagle, and sea eagles)–they don’t stay in the water long and predominantly nest over land (though some may nest on islands within lakes), and therefore aren’t classified here–they’re under the ‘raptor’ page.
Since there are numerous orders and families that can be classified as ‘water birds’, the only set ‘characteristic’ is that they spend a large amount of time on (or in), or near the water.