The white-throated kingfisher (Halcyon smyrnensis) also known as the white-breasted kingfisher.
I also often find this larger bird in Mai Po. This one below appeared when I was taking pictures of a Long-tailed shrike ,and it came and pushed the other bird off its perch.
The song is a loud ringing “kilililili” while its regular call, mostly uttered in flight, is a loud chattering “kra-kra-kra-kra-kra” laugh.
Here it is swooping across a river in the early morning light.
This kingfisher is not tied to water and occupies all kinds of habitats including gardens, parks, homesteads, and woodlands.
Here is a shot of the underside of his wings...and those ripples in the water? those are the fish he is hunting....