In my opinion, the best time of year to shoot docks is April/May. The depth I look for varies on what the fish tell me but I typically start around 3-4 ft deep. The more shade there is the shallower I will try.
April and May are best. I catch some fish through July on docks. They get back on them again late Sept and Oct as well. Livescope has taken all the guess work out of finding the good docks anymore. Cruise a bank on high till you find em. When you do that's where they are when they're on docks!