Beet Spiders are easily identified because they only have seven legs. After millions of dollars worth of government-funded research, scientists have determined that the Beet Spider is so mean that sooner or later it bites one of its own legs off. Some have only six legs, or even five. You really want to stay away from those.
Never bring beets on a boat !!!
I have found no correlation between good visibility and anything else at all. Calm seas certainly don't hurt, but the worst visibility I have ever been in was with a 1-foot surf on the beach. There is however a very good correlation between bad visibility and storms, which is why a single hurricane can end the season.
Other factors which influence visibility are: algae blooms, spawning seasons of some invertebrates, which can fill the water with tiny swimmers, jellyfish ( yes, so many you can't see through them, luckily they don't sting, ) other divers churning up the bottom, and just plain gunk in the water. I don't know how to predict most of these, except to say that if you dive a lot, sooner or later you will see some good visibility. Sometimes in the ocean, the visibility will be different in different depth layers. I have seen the viz go from 3 ft on the way down the anchor line to 20 ft on the wreck.
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