Here is a video review of a USB Endoscope (bore-scope) you can buy off E-Bay for less than $20 shipped:
Here is a link to the Ebay auction:
This is the cheapest auction I could find for this product, and it even includes a 90-degree mirror attachment, which is a nice touch.
I'll buy one after I've moved my boat closer to home. Heck, once I've moved it, it will be my home! For now, I'm not spending money on anything that doesn't contribute to that goal!