This is an easy trick for Java tool to make water refflections, but it can be also used to make another kind of reflecctions like some views on mirrors...
ok, first we make a background ( i will make an easy one as an example).
we make a new layer.
in this new layer we make the drawing, here i made just shadows of the ground and a figure in the middle with some stars in the sky...
when you be finished with your drawing , go to layers options and select "duplicate" , it will appear with the same name and "copy" at the end...
with this copied layer we will do this:
go to "effects" and select "flip vertical"
we will move the whole layer to put it where we want with the "move" tool
for example like this...
now we will merge all layers, in layers options...
select the "smudge" tool...
and use it in the part of the bottom, to make the effect of the waves...
You can use this in many ways, and with alot of layers... this is just a simple example to show the idea of the technique.
Hope it be helpfull ^^