Milfoil is lurking underneath the water in Lake Washington.
The invasive plant hitched a ride on boats to the area, has settled into the water and is growing fast -- so fast it would eventually suck up most of the water's oxygen.
That's if lake officials don't put a stop to this plant's progress. The first round of attacks Monday is closing Meydenbauer Beach Park until 7 p.m. Tuesday.
Clyde Beach Park will close from 7 a.m. Tuesday to 7 a.m. Wednesday, and then Newcastle Beach closes from 7 a.m. Wednesday through 7 a.m. Thursday.
Even though the beaches are closed, the parks will remain open.