Derived from Water Footsteps by EminYILDIRIM
https://freesound.org/people/EminYILDIRIM/sounds/608663/
http://creativecommons.org/licenses/by/4.0/

And footstep-concrete.wav by swuing
http://www.freesound.org/people/swuing/sounds/38873/
http://creativecommons.org/licenses/by/3.0/