Another option is Hope Springs Marina. It's about 5 miles off
I-95, exit 140. http://www.hopespringsmarina.com/
Leaving the marina there is a 5 minute no wake then follow the channel markers out of Aquia Creek. It will put you out on the Potomac about a mile north of Tims. Probably a leisurly 15-20 minute boat ride.
Driving the truck from Hope Springs to Tims would be about 30 min (in the morning with light traffic).