On a recreational boat and yacht marine pests could hitch a ride on:
Ships and commercial boats have exactly the same problems with hull fouling as international ships. Local cargo ships still rely of pumping ballast water to evenly distribute weight across the ship.
Biofouling of all ships and boats starts very quickly. The only way of slowing this down is to paint the hull with biofouling paint and clean the hull when it becomes encrusted with marine life. Removing the encrusted life must be done anyway because it dramatically slows the vessel.