Initiating inverts is not the hard part. Your body follows your head, and you rotation depends on your handle position.
Come in hot and with lots of load, get good pop, turn your head, look back over your lead shoulder and leave it there. If you move your head back straight, it will stall your rotation. Once you see the water, follow it with your eyes and spot the landing.
If you are rotating to fast, allow the handle to move up slightly towards you chest to slow it down. If you are rotating too slow, pull it in to your waist and pull your knees up a little to speed it up.