I am about to purchase a Garmin 3006C multifunction chartplotter which has an AV input. I want to get a camera suitable for mounting on the transom of my boat for viewing coral reefs, shallow fishing spots, etc. Any suggestions?

is that underwater or on the front of the boat?

This is a very good one, on the high end.

http://www.extremecctv.com/products/index.cfm?img=10