My Specialized FSR at just under 40lbs weight the very efficient electric Solar-Cross (one horsepower) is able to remain on top the Pacific Ocean sand along English Bay in Vancouver. Only approx. 1-2 feet away from the ocean waters, sinking deep into the wet beach sand is an hard escape, but easy to maintain speed once in motion. I did try just pedaling and I was not having any success at getting upto a stable speed..
Throttle was about half twist or 0.5 horsepower.
Drive sprocket was set on the larger of the two front rings (38T)
Stabilized filter version
http://www.youtube.com/watch?v=N_2HKVM_5uo