I did the night snorkel 2 years ago and it was awesome. We got to see so much more wildlife. The basket starfish were really cool. As long as we had at least 4 people they said we were going. It was 35 per when I did it but well worth it.
We did the night snorkel at CSA. We left right at sunset, and, as luck would have it, an enormous full moon was rising over the Sea at the same time. It was a memory of a lifetime. The trip lasts about an hour. They give each participant a large flashlight, and there is a guide to show you around. We saw several large lobsters, which we never saw during the day.