Some could get themselves
 a Water Dragon Egg to get
themselves a Water Dragon. To 
hatch an Water Egg, place 3x3 
blocks of Wet Bone Pile. 
Place the Water Egg in the center,
then place a water source
 nearby and wait 2 days.
If your Water Dragons age is 20 years or more
you can ride it, but the Water Dragon
is not ready to fight, it's age must
be 45 years or more