I want to purchase a good computer based charting program that has details of offshore structures out to the canyons.
Anyone have any suggestions?

I've used Maptech in the past. They have different solutions available depending on what you want to do (Offshore Navigator, Chart Navigator, Chart Navigator Plus, etc).

Their main office is local (Amesbury, MA).

I also have Garmin's Homeport software that lets me connect the SD card from my chartplotter to my home pc....and all of the G2 charts are accessible (as well as my waypoints, tracks, routes, etc)

I want to purchase a good computer based charting program that has details of offshore structures out to the canyons.
Anyone have any suggestions?

The software is irrelevant, the charts (bsb vs vector) are what you need to look into.

Went to an MSBA seminar this winter that Riptide was doing and I want to say it was Ray Marine and the Navionics software that he uses that give unbelievable detail today in terms of underwater topography. You can even get it on an iphone or droid. It was pretty amazing. They showed old std software of Scorton Creek at one point and then the enhanced version and it was taken to a whole new level. Maybe someone else can chime in as I honestly forget the details.

Get the bathyrithmetic <sp?> charts, world of difference from the regular charts.