Should have called it "field hockey", check this wikipedia article for details, its just that Ice hockey is a bit rarer over here (not unknown just if you said "hockey" to someone over here they would probably think field rather than ice so I tend to think in terms of clarifying that when there is a possibility of confusion by people from countries where its the other way around, but I didn't know the proper name for it (I was still half-asleep when I wrote that). I haven't played water polo but looking at the wiki article they do share similarities, there's a wiki article here if you're interested in further details.