They can choke a lake or river, causing fish to die and the local economies dependent on that water supply to stagnate.
Texas Parks and Wildlife biologists are taking an aggressive approach to fighting the aquatic invaders.
Giant Salvinia, an exotic plant from South America is causing major problems on several Texas lakes.
Even though Salvinia will never be eradicated, biologists are trying to reduce the coverage down to a more manageable area.
Many times these aquatic invaders are transported from lake to lake by boat trailers.
In addition to clean-up campaigns, the Texas Parks and Wildlife Department is trying hard to educate Texans.