Is it seaweed, a plastic bag, no it's a huge jellyfish

While eating on the upstairs balcony of Point Loma Seafood, 2805 Emerson St., in Point Loma, CA my nephew saw something huge in the harbor, quite a ways in, too. He said it's a jellyfish, I said, nay, it's too big and too dark, maybe it's seaweed. Well he was right, it was the biggest, darkest jelly we had ever seen personally. I took the pic on July 11, 2012, but since I transferred it to my camera today, 8/9/12, the 'Date of sighting' won't accept my photo date.