Answer:
My second is performed by my first, and it is thought a thief by the marks of my whole might be caught.
A little pool with two layers of wall around it. One white and soft and the other dark and hard. Amidst a light brown grassy lawn with an outline of a green grass.
What can run but can’t walk?
Don't do this in the shallow end.
I can be short and sometimes hot. When displayed, I rarely impress.
They are many and one, they wave and they drum, Used to cover a state, they go with you everywhere.