The reason why their so invasive is because they attach to propellers of a boat or on the bottom of the boat. When the zebra mussels do this they fall off and attach themselves to rocks which later on they end up cutting people's feet and infecting those who step on them. Zebra mussels can also clog draining pipes or regular pipes and can cause damage to these pipes.
Zebra mussels travel places is because they attach to the bottom of the boats