The Rat & The Drainpipe.

Water blasting is a good way to clean blocked culverts.
A "rat" which has forward and backward facing jets is fed up the pipe.
Some rats have a spinning vane that can cut tree roots.
A lot of water at about 2,500 lb pressure shifts most things.
Stones shotblasting your legs can be a bit painful.

It is a great activity to watch however.