How do I get the fish to come in range?
This is the whole essence of spearfishing! A good spearo will always be learning new tricks.
Bass in particular are very curious. One technique which takes advantage of this is the agachon or aspetto technique. Basically this consists of diving down and lying on the bottom, hidden in the weed or behind a rock with the gun ready, waiting for a fish to appear in range.
Any fish in the area will sense your descent to the bottom, and come in to find out what this strange object is.The trick is not to do anything to scare them. Bass hate being looked at directly.
Moving the gun towards a fish will also often spook it, it is better to anticipate its movements, and point the gun at where it will be in a few seconds. Needless to say all movements should be smooth and fluid.