Glad you like them! I continue to let Cindy know her work has an appreciative audience.
I've been on the Bay since 1976 and that's the first time I've seen numbers of stingrays like that. We were both standing up on the TI so we could see them better as we glided through them. Cindy shot a lot more additional schools of them but only posted the best footage of what she collected. We figure we saw a couple hundred (or more!) stingrays in an area that was about a mile long and 12 feet deep - they were all close to the surface, moving slowly and would slowly scatter as we got close to them.
We do have sea nettles (http://en.wikipedia.org/wiki/Sea_nettle
) that will deliver a good sting, but nothing remotely close to a Portuguese Man o' War or your deadly box jellies.