I run by and walk by and drive by the Potomac several times each week, but before last month I'd never been on the Potomac. You see the fancy boats docked at the Georgetown waterfront and think that boarding one of those will never be a possibility, but a short walk down the waterfront and you can get your own vessel for the Potomac for $20.
I went with some coworkers right after work on a Tuesday afternoon. We just walked up, signed a waiver, surrendered an ID, picked out a life jacket and jumped on the river. I was the only one in my group that had paddle boarded before so they gave us a 30 second overview and pushed us off. Paddling with the current and mini waves was more challenging than when I SUP'd in a pond, but it wasn't hard to adjust and tool around the river.
We spent about an hour and a half on the river* before we were ready for some burgers and beer at the Georgetown legendary college bar, Tombs.
*out of the five of us only one guy spent anytime IN the river.