Just out of curiosity, and if you can recall, what time of day was your best snorkeling experience. I mean, when are the sea creatures most likely to be active?
Morning is the best, but another really good time is just before sunset. There's a lot of activity at this time of day. For example, this is usually when we have seen tarpon and snapper feeding on silversides, which can be exciting to watch.
It's like looking in your soup and finding a whole different alphabet.
For finding some creatures that blend in well with their surroundings, I prefer mid-day. It's easier for me to distinguish them from the background in the brighter light.
I agree with Pickle, mid day gives the best lighting. Haven't been out before 10, but after 2, the sun starts bouncing off the water as much as it penetrates.