Fill a large plastic peanut butter jar with coarse, dry builder's sand and keep it in your tow vehicle. A handfull of sand broadcast on a slick ramp will help prevent nasty falls. This is especially useful in tidal rivers and hydroelectric impoundments where water level at the ramp changes regularly and leaves a slick surface.
A few handfuls of sand under and in front of spinning tires will provide additional traction.
Peanut butter jars are handy for lots of things.