From the looks of the transom there has been some damage were it joins the hull. I would firstly try to ascertain what this damage is. If the transom has been ripped off or pull away from the hull in the past that is bad. If it is just a case of a puncture or wear to the hull that is not so bad. I also notice there is a drain plug there. Best case would be the leak coming from that. Once you are sure the transom is not structurally damaged or the drain plug is not the cause. Sand back the paint and damaged fibreglass. Buy a fibreglass repair kit and with a stiff brush apply the layers of fibreglass. I am sure you will find plenty of advice on fibreglass repairs
