One June night while on a night sail from Boston to P-Town through a light fog, there were phosphorescent jelly fish everywhere... It was mesmerizing to watch them glow especially bright in our wake.
We were motoring (no wind) and I was at the helm at about 02:00. I noticed a green spark approaching us from dead ahead. At first I thought it was a cinder, blowing in the wind, but it was green. it looked to be about the size of a humming bird, and was the phosphorescent color of the jellyfish. What ever it was, it buzzed through our shrouds, then chased us for about a minute. It would fall away from our stern, then loop and approach us again. It was NOT a firefly, because it was way too big, and it didn't flash, but glowed steadily.
My watch mate and I looked at each other with a "WTF?" expression. We both saw it, and talked about it for a while. We never figured out what it was.
And, I know what you're thinking - NO drugs of any kind were involved...