and it's in the area of a single through hull the action will be so fast that the boat is likely to sink before you notice the problem. With a bonded system the "action" is spread across all of the underwater parts and connected to a zink. You can monitor the zink and "read" what's going on by the longevity of the zink. Unless you want to install a zink on every fitting, which is problematic in itself, bonding makes mose sense to me.