Naturally, you'll want to put in all of the agencies from the Neck, plus Calvert, Charles, and St. Mary's Counties in Maryland. Keep in mind that 80% of what you can receive is based on the antenna. If you're using the stock "rubber-ducky" antenna that came with the scanner, you're going to have limited reception, espically on the low-band frequencies.
Since you're near the water, you might try:
Virginia Department of Game and Inland Fisheries
Virginia Marine Resources Commission
United States Coast Guard
The standard marine channels
Don't forget the MSP helicopters!
Hope this helps...