agreed. mine is really shy about letting people see him on his dock. the moment he hears someone coming (even in a different room), he'll dive off like bat out if h***.
the water depth looks alright, although they are definitely aquatic turtles and can stand (and like) much deeper water.
i'm not sure if i missed it, but what sortof filtration do you have for him? also, you will want to make sure any substrate/gravel you have is bigger than his head, otherwise he may try to eat it, get impacted and die.