Yes, the thing to do is find the magnitude, the source and the origination. Let's assume that in that puddling location it is fresh water and that would indicate that the source is either a rain leak or a fresh water system leak. Now you can either drain the fresh water tank or wait for a dry period with no rain. The idea is to dry up the pool of water and see under what single circumstance it reappears. If it does not rain and the puddle is dry then the leak is likely a rain one. To corroborate you may hose down the whole port side of the boat preferably in sections starting from the stern. The likely originating locations would be portholes, deck fixtures, deck drain hoses, anchor locker, stanchions, pulpit, sink drains, etc. Any suspect deck fixture and stanchions should be rebbeded. The leak could be compound so the magnitude may indicate whether it is originating from one or more locations. If the source is on the fresh water system then the leak could be in the tank, hoses, fixtures or connections. Start checking for any hoses or fixtures near the pooling. Some will dry the spot and then lay talcum powder all around the area to determine from which direction the water may be coming. I would advice against removing any of the paneling until you are certain of the originating point and it becomes necessary. The majority of deck leaks can be corrected from the deck without the need to remove paneling. On the unlikely possibility that the pooling is salt water then you would need to look at deck/hull joint or sink drain hoses. It will be assumed that any other salt water intrusion will flow to the bilge. Hunting leaks is not easy, so being patient and methodically following the source and origination is the way to do it. Hope this gives you an idea on what needs to be done.