During the months of May to September, Potomac Riverboat Company lets you cruise with your pooch. These fun boat trips are offered during those warm months and include a 40-minute tour of Alexandria's seaport. Ships set sail every Thursday at 7, 8, and 9 p.m. Humans can come to play with the dogs or bring or borrow a pet to make the trip – people pay $12 and pups ride free.