Montana was invaded last summer. Not by land, not by air, but by water. A microscopic alien showed up in water samples from the Tiber Reservoir, opening the door to a wide range of potentially devastating impacts for Montana's fisheries, outdoor enthusiasts and industries. What happens if Montana fails to stop the coming invasion of zebra and quagga mussels threatening the state's water bodies? MTPR's Nicky Ouellet looks into Montana's future (or one possible future) to see how the invasive mussels changed the Great Lakes region, and examines Montana's efforts to detect and prevent their spread. Learn more about Montana's underwater invaders, on SubSurface, a new podcast from Montana Public Radio.