Probably the best way of describing it is in the same way as it was described/demonstrated to me:
Soft ground - the aircraft will sink easier the slower that you taxi.
Going through isolated known soft patches one keeps the speed up to stop getting stuck.
Aquaplaning - throwing a stone across a pond. The faster the stone is travelling -it will not sink.
Aircraft tyres are no different.
https://www.google.co.uk/url?sa=t&rc...91071109,d.ZWU