Water hyacinths can grow so densely that it completely blocks rivers and canals, and the water is no longer visible. Besides being an nuisance for navigation, it also hinders shipping traffic, as plants easily get stuck in the blades of a boat's propeller.

This actually led to the invention of the longtail boat, which has a motor with a propeller on a long shaft, specially designed to avoid floating rubble and which can easily be lifted out of the water and cleared if the propeller gets stuck in the floating foliage.