Well Patrick,
The more I look at your photos, the more I'm believing you do not have a shelf but rather your tank rests on the hull itself. I would think there are rubber strips underneath the tank for chafe protection but the water entering works it's way around the tank itself and now drains through the penetration you drilled.
While there are different opinions to tank installation, keeping the compartment as dry as possible seems to be a universally accepted concept.
Here's a 245 tank that sat in water.
This is my tank from my 91. The leak was under the rubber mounting in front of the tank. This was from the standing water in the front bilge. The P.O. apparently didn't keep the bow elevated high enough during storage.
I would suggest you monitor your tank from time to time for the fuel smell and the sheen on the water now draining from the bilge.
As to your photos:
You might want to read this thread and begin using the Forum's Photo Gallery. It works very well and makes life simple when loading and posting photos.
http://classicaquasport.com/smf/index.php?topic=12725.0Good luck.