Answer:
The ninja turtles call this place home, as do mythical alligators.
A spent round or a slimy critter.
It can be white or blue or black, Humped or have a horn. And when it talks it sings its menuets, as it's travelling the depths.
Face with a tree, skin like the sea. A great beast I am. Yet vermin frightens me.
A warrior amongs the flowers, He bears a thrusting sword. Able and ready to use, To guard his golden hoard.
What is always coming but never arrives?