Answer:
I am round as a bowl, deep as a tub, but all the world's water couldn't fill me up.
Large as a mountain, small as a pea, Endlessly swimming in a water-less sea.
Different lights do make me strange, thus into different sizes I will change.
Today he is there to trip you up. And he will torture you tomorrow. Yet he is also there to ease the pain, when you are lost in grief and sorrow.
Each of these ends in a kettle full of precious metal and the double variety is quite awesome
Both a currency and an antlered male. What is it?