Travelzoo offers a Capitol River Cruises 45-Minute Narrated Potomac River Cruise in Washington D.C. with prices starting from $8. Or get this cruise for two for $15. That's tied with last week's mention as a savings of at least $7 and the lowest price we could find for any such cruise. Tours depart hourly from 11 am to 7 pm Monday through Friday. Book this travel deal by September 30 for stays through the same period.