"Rare jellyfish appears in San Diego Bay"

From LA Times Blogs:
A rare species of jellyfish, distinguishable by its black color and long tentacles, is being spotted along a stretch of San Diego Bay popular with boaters.

With the formal name of Chrysaora achlyos, the so-called "black jellyfish" range from Monterey Bay to the tip of Baja California and seem to be making increasing appearances in San Diego-area waters, perhaps because the water is getting warmer.

This summer, they have been spotted near Shelter Island.

Stepping on the jellyfish, or otherwise coming into contact with one, can be a painful experience. The creatures have nettles that sting and immobilize their prey. Even a dead jellyfish carries a sting -- not enough to kill a human, but enough to be unpleasant.

The jellyfish's body can measure 3 feet in diameter, and the tentacles can be 25 feet or more in length.

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The black jellyfish (which can weigh 50 pounds) seem to like the Coronado beaches:

Lifeguards Continue to Deal With Influx of Jellyfish