UNDER DA SEA: If, like Seattlest, you are fascinated with underwater life, tonight's your night to revel in the glories of the deep ocean. Seattle Symphony will be playing as a giant screen shows you images from the BBC series The Blue Planet. 7:30 // Benaroya Hall // $17-75 B.Y.O.B. (BRING YOUR OWN BAG): City Council will be discussing this whole bag tax thing tonight at their meeting, and you should go help them discuss......