Just when you thought it was safe to go back to the TV set: Yes, it’s summer, and Shark Week again, on the Discovery Channel. All this week, the network is filling the water, and its air, with documentaries about sharks – some serious, others about as fanciful as a Sharknado Syfy telemovie. Tonight’s lineup, for example,  begins at 7 p.m. ET with Great White Serial Killer Lives, followed by Phelps vs. Shark: Great Gold vs. Great White at 8 ET (relax: the illustration is Photoshopped), Shark-Croc Showdown at 9 ET, and The Great Hammerhead Invasion at 10 ET. And that’s just tonight. Personally, I think much of this Shark Week coverage is nothing but underwater racism. Even in this allegedly enlightened era, it’s all about the Great White…