bioluminescent jellyfish swarm

I do not know the type of jelly these were. They ranged in size from a penny to circumference of a tennis ball. As the tide was coming in at my home the jellies were lighting up a soft blue color, sometimes showing rings, as they were drifting over a couple of oyster beds. What a beautiful sight! Estimating the number is difficult (probably more than a thousand) but there were 10-20 lighting up at any one time and the tide was moving at about two seconds per foot and this has been going on for over an hour.