This week, "Invasion of the Bay Snatchers": Combating non-native aquatic species in the bay is not just an exercise in aestheticism. There's very real danger in the newcomers. The names and descriptions of such invaders as the Asian swamp eel, hydrilla water weed, Asian or "Overbite" clam, quagga mussels, spartina grass, and the so-called nuclear worm (hot pink, six feet long, from Vietnam) are bad enough, but the damage they do is even worse: clogging pipes, choking off water surfaces, altering the food chain, introducing parasites, etc. And just like human beings, seemingly everyone in the underwater creature and vegetation world wants to move to the Bay Area - they arrive on ships' hulls, in ballast water, as fishing bait. What's a marine biologist to do? Writer Eric Simons ventures down to the shoreline to find out.